Combining Philosophers

All the ideas for J.P. Moreland, Jan Westerhoff and Michael Devitt

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53 ideas

2. Reason / B. Laws of Thought / 6. Ockham's Razor
Epistemological Ockham's Razor demands good reasons, but the ontological version says reality is simple [Moreland]
     Full Idea: Ockham's Razor has an epistemological version, which says we should not multiply existences or explanations without adequate reason, and an ontological version, which says reality is simple, and so a simpler ontology represents it more accurately.
     From: J.P. Moreland (Universals [2001], Ch.2)
     A reaction: A nice distinction. Is it reality which is simple, or us? One shouldn't write off the ontological version. If one explanation is simpler than the others, there may be a reason in nature for that.
5. Theory of Logic / F. Referring in Logic / 1. Naming / a. Names
We negate predicates but do not negate names [Westerhoff]
     Full Idea: We negate predicates but do not negate names.
     From: Jan Westerhoff (Ontological Categories [2005], §88)
     A reaction: This is a point for anyone like Ramsey who wants to collapse the distinction between particulars and universals, or singular terms and their predicates.
7. Existence / D. Theories of Reality / 1. Ontologies
Existence theories must match experience, possibility, logic and knowledge, and not be self-defeating [Moreland]
     Full Idea: A theory of existence should 1) be consistent with what actually exists, 2) be consistent with what could exist, 3) not make existence impossible (e.g. in space-time), 4) not violate logic, 5) make knowing the theory possible.
     From: J.P. Moreland (Universals [2001], Ch.6)
     A reaction: A nice bit of metaphilosophical analysis. I still doubt whether a theory of existence is possible (something has to be 'given' a priori), but this is a good place to start the attempt.
7. Existence / E. Categories / 1. Categories
How far down before we are too specialised to have a category? [Westerhoff]
     Full Idea: How far down are we allowed to go before the categories become too special to qualify as ontological categories?
     From: Jan Westerhoff (Ontological Categories [2005], Intro)
     A reaction: A very nice question, because we can't deny a category to a set with only one member, otherwise the last surviving dodo would not have been a dodo.
Maybe objects in the same category have the same criteria of identity [Westerhoff]
     Full Idea: There is an idea that objects belonging to the same category have the same criteria of identity. This view was first explicitly endorsed by Frege (1884), and was later systematized by Dummett (1981).
     From: Jan Westerhoff (Ontological Categories [2005], Intro)
     A reaction: This approach is based on identity between equivalence classes. Westerhoff says it means, implausibly, that the resulting categories cannot share properties.
Categories are base-sets which are used to construct states of affairs [Westerhoff]
     Full Idea: My fundamental idea is that 'form-sets' are intersubstitutable constituents of states of affairs with the same form, and 'base-sets' are special form-sets which can be used to construct other form-sets. Ontological categories are the base-sets.
     From: Jan Westerhoff (Ontological Categories [2005], Intro)
     A reaction: The spirit of this is, of course, to try to achieve the kind of rigour that is expected in contemporary professional philosophy, by aiming for some sort of axiom-system that is related to a well established precise discipline like set theory. Maybe.
Categories are held to explain why some substitutions give falsehood, and others meaninglessness [Westerhoff]
     Full Idea: It is usually assumed of ontological categories that they can explain why certain substitutions make a statement false ('prime' for 'odd'), while others make it meaningless ('sweet' for 'odd', of numbers).
     From: Jan Westerhoff (Ontological Categories [2005], §05)
     A reaction: So there is a strong link between big ontological questions, and Ryle's famous identification of the 'category mistake'. The phenomenon of the category mistake is undeniable, and should make us sympathetic to the idea of categories.
Categories systematize our intuitions about generality, substitutability, and identity [Westerhoff]
     Full Idea: Systems of ontological categories are systematizations of our intuitions about generality, intersubstitutability, and identity.
     From: Jan Westerhoff (Ontological Categories [2005], §23)
     A reaction: I think we might be able to concede this without conceding the relativism about categories which Westerhoff espouses. I would claim that our 'intuitions' are pretty accurate about the joints of nature, and hence accurate about these criteria.
Categories as generalities don't give a criterion for a low-level cut-off point [Westerhoff]
     Full Idea: Categories in terms of generality, dependence and containment are unsatisfactory because of the 'cut-off point problem': they don't give an account of how far down the order we can go and be sure we are still dealing with categories.
     From: Jan Westerhoff (Ontological Categories [2005], §27)
     A reaction: I don't see why this should be a devastating objection to any theory. I have a very clear notion of a human being, but a very hazy notion of how far back towards its conception a human being extends.
Categories can be ordered by both containment and generality [Westerhoff]
     Full Idea: Categories are usually not assumed to be ordered by containment, but also be generality.
     From: Jan Westerhoff (Ontological Categories [2005], §02)
     A reaction: I much prefer generality, which is responsive to the full picture, whereas containment seems to appeal too much to the orderly and formalised mind. Containments overlap, so we can't dream of a perfectly neat system.
7. Existence / E. Categories / 2. Categorisation
The aim is that everything should belong in some ontological category or other [Westerhoff]
     Full Idea: It seems to be one of the central points of constructing systems of ontological categories that everything can be placed in some category or other.
     From: Jan Westerhoff (Ontological Categories [2005], §49)
     A reaction: After initial resistance to this, I suppose I have to give in. The phoenix (a unique mythological bird) is called a 'phoenix', though it might just be called 'John' (cf. God). If there were another phoenix, we would know how to categorise it.
7. Existence / E. Categories / 3. Proposed Categories
All systems have properties and relations, and most have individuals, abstracta, sets and events [Westerhoff]
     Full Idea: Surveyed ontological systems show overlaps: properties and relations turn up in every system; individuals form part of five systems; abstracta, collections/sets and events are in four; facts are in two.
     From: Jan Westerhoff (Ontological Categories [2005], §02)
     A reaction: Westerhoff is a hero for doing such a useful survey. Of course, Quine challenges properties, and relations are commonly given a reductive analysis. Individuals can be challenged, and abstracta reduced. Sets are fictions. Events or facts? Etc.
7. Existence / E. Categories / 5. Category Anti-Realism
Ontological categories are like formal axioms, not unique and with necessary membership [Westerhoff]
     Full Idea: I deny the absolutism of a unique system of ontological categories and the essentialist view of membership in ontological categories as necessary features. ...I regard ontological categories as similar to axioms of formalized theories.
     From: Jan Westerhoff (Ontological Categories [2005], Intro)
     A reaction: The point is that modern axioms are not fundamental self-evident truths, but an economic set of basic statements from which some system can be derived. There may be no unique set of axioms for a formal system.
Categories merely systematise, and are not intrinsic to objects [Westerhoff]
     Full Idea: My conclusion is that categories are relativistic, used for systematization, and that it is not an intrinsic feature of an object to belong to a category, and that there is no fundamental distinction between individuals and properties.
     From: Jan Westerhoff (Ontological Categories [2005], Intro)
     A reaction: [compressed] He calls his second conclusion 'anti-essentialist', but I think we can still get an account of (explanatory) essence while agreeing with his relativised view of categories. Wiggins might be his main opponent.
A thing's ontological category depends on what else exists, so it is contingent [Westerhoff]
     Full Idea: What ontological category a thing belongs to is not dependent on its inner nature, but dependent on what other things there are in the world, and this is a contingent matter.
     From: Jan Westerhoff (Ontological Categories [2005], §89)
     A reaction: This is aimed at those, like Wiggins, who claim that category is essential to a thing, and there is no possible world in which that things could belong to another category. Sounds good, till you try to come up with examples.
8. Modes of Existence / B. Properties / 13. Tropes / a. Nature of tropes
Tropes are like Hume's 'impressions', conceived as real rather than as ideal [Moreland]
     Full Idea: Tropes are (says Campbell) substances (in Hume's sense), and indeed resemble his impressions conceived realistically rather than idealistically.
     From: J.P. Moreland (Universals [2001], Ch.3)
     A reaction: An interesting link. It doesn't get rid of the problem Hume has, of saying when two impressions are the same. Are they types or tokens? Trope-theory claims they are tokens. Hume's ontology includes 'resemblance'.
8. Modes of Existence / B. Properties / 13. Tropes / b. Critique of tropes
A colour-trope cannot be simple (as required), because it is spread in space, and so it is complex [Moreland]
     Full Idea: A property-instance must be spread out in space, or it is not clear how a colour nature can be present, but then it has to be a complex entity, and tropes are supposed to be simple entities.
     From: J.P. Moreland (Universals [2001], Ch.3)
     A reaction: Seems a fair point. Nothing else in reality can be sharply distinguished, so why should 'simple' and 'complex'?
In 'four colours were used in the decoration', colours appear to be universals, not tropes [Moreland]
     Full Idea: If a decorator says that they used four colours to decorate a house, four tropes is not what was meant, and the statement seems to view colours as universals.
     From: J.P. Moreland (Universals [2001], Ch.3)
     A reaction: Although I am suspicious of using language to deduce ontology, you have to explain why certain statements (like this) are even possible to make.
8. Modes of Existence / D. Universals / 1. Universals
Realism doesn't explain 'a is F' any further by saying it is 'a has F-ness' [Devitt]
     Full Idea: Realists feel that the one-place predication 'a is F' leaves something unexplained, yet all that is offered is a two-place predication (a relational statement). There is an equal problem about 'a having F-ness'.
     From: Michael Devitt ('Ostrich Nominalism' or 'Mirage Realism'? [1980], p.97)
     A reaction: I think this is a key argument on the nominalist side - the denial that the theory of universals actually makes any progress at all in giving an explanation of what is going on around here. Platonist have the problem of 'partaking'.
One realism is one-over-many, which may be the model/copy view, which has the Third Man problem [Moreland]
     Full Idea: One version of realism says that the universal does not enter into the being of its instances, and thus is a One-Over-Many. One version of this is the model/copy view, but this is not widely held, because of difficulties such as the Third Man Argument.
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: This presumably arises if the model is held to have the properties of the copy (self-predication), and looks like a bad theory
Realists see properties as universals, which are single abstract entities which are multiply exemplifiable [Moreland]
     Full Idea: Traditional realism is the view that a property is a universal construed as a multiply exemplifiable abstract entity that is a numerically identical constituent in each of its instances.
     From: J.P. Moreland (Universals [2001], Ch.4)
     A reaction: Put like that, it seems hard to commit oneself fully to realism. How can two red buses contain one abstract object spread out between them. Common sense says there are two 'rednesses' which resemble one another, which is a version of nominalism.
If properties are universals, what distinguishes two things which have identical properties? [Moreland]
     Full Idea: If properties are universals, what account can be given of the individuation of two entities that have all their pure properties in common?
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: Is this a big problem? Maybe only a space-time location can do it. Or, in the nice case where the universe is just two identical spheres, it may be impossible.
8. Modes of Existence / D. Universals / 2. Need for Universals
The traditional problem of universals centres on the "One over Many", which is the unity of natural classes [Moreland]
     Full Idea: Historically the problem of universals has mainly been about the "One over Many", which involves giving an account of the unity of natural classes.
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: This still strikes me as the main problem (rather than issues of language). If universals are not natural, they must be analysed as properties, which break down into causation, which is seen as a human convention.
Evidence for universals can be found in language, communication, natural laws, classification and ideals [Moreland]
     Full Idea: Those who believe in universals appeal to the meaningfulness of language, the lawlike nature of causation, the inter-subjectivity of thinking, our ability to classify new entities, gradation, and the need for perfect standards or paradigms.
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: Of these, language and communication ought to be explicable by convention, but classification and natural laws look to me like the best evidence.
8. Modes of Existence / D. Universals / 3. Instantiated Universals
The One-In-Many view says universals have abstract existence, but exist in particulars [Moreland]
     Full Idea: Another version of realism says is One-In-Many, where the universal is not another particular, but is literally in the instances. The universal is an abstract entity, in the instances by means of a primitive non-spatiotemporal tie of predication.
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: This sounds like Aristotle (and is Loux's view of properties and relations). If they are abstract, why must they be confined to particulars?
8. Modes of Existence / D. Universals / 4. Uninstantiated Universals
How could 'being even', or 'being a father', or a musical interval, exist naturally in space? [Moreland]
     Full Idea: Many properties (being even) and relations (musical intervals, being a father) are such that it is not clear what it would mean to take them as natural things existing in space.
     From: J.P. Moreland (Universals [2001], Ch.4)
     A reaction: 'Being even' certainly seems to be a property, and it is a struggle to see how it could exist in space, unless it is a set of actual or potential brain states.
Maybe universals are real, if properties themselves have properties, and relate to other properties [Moreland]
     Full Idea: Realism about universals is supported by the phenomenon of abstract reference - that is the fact that properties themselves have properties ('red is a colour'), and stand in relation to other properties ('red is more like orange than like blue').
     From: J.P. Moreland (Universals [2001], Ch.1)
     A reaction: While a property may be an obviously natural feature, properties of properties seem more likely to be the produce of human perception and convention. It is a good argument, though.
A naturalist and realist about universals is forced to say redness can be both moving and stationary [Moreland]
     Full Idea: If a property is held to be at the location of the particular, then if there are two objects having the same property, and one object is stationary and the other is moving, the realist is forced to say that the universal is both moving and at rest.
     From: J.P. Moreland (Universals [2001], Ch.4)
     A reaction: The target of this comment is D.M.Armstrong. The example nicely illustrates the problem of trying to combine science and metaphysics. It pushes you back to Platonism, but that seems wrong too…
There are spatial facts about red particulars, but not about redness itself [Moreland]
     Full Idea: When one attends to something existing in space, one attends to an instance of redness, not to redness itself (which is a colour, which resembles orange). The facts about red itself are not spatial facts, but are traditionally seen as a priori synthetic.
     From: J.P. Moreland (Universals [2001], Ch.4)
     A reaction: This is the fact that properties can themselves have properties (and so on?), which seems to take us further and further from the natural world.
8. Modes of Existence / D. Universals / 6. Platonic Forms / a. Platonic Forms
Redness is independent of red things, can do without them, has its own properties, and has identity [Moreland]
     Full Idea: Four arguments for Platonism: 1) there are truths about redness (it's a colour) even if nothing red exists, 2) redness does not depend on particulars, 3) most universals are at some time not exemplified, 4) universals satisfy the criteria of existence.
     From: J.P. Moreland (Universals [2001], Ch.6)
     A reaction: This adds up to quite a good case, particularly the point that things can be said about redness which are independent of any particular, but the relationships between concepts and the brain seems at the heart of the problem.
8. Modes of Existence / E. Nominalism / 1. Nominalism / a. Nominalism
Moderate nominalism attempts to embrace the existence of properties while avoiding universals [Moreland]
     Full Idea: Moderate nominalism attempts to embrace the existence of properties while avoiding universals.
     From: J.P. Moreland (Universals [2001], Ch.2)
     A reaction: Clearly there is going to be quite a struggle to make sense of 'exists' here (Russell tries 'subsists). Presumably each property must be a particular?
8. Modes of Existence / E. Nominalism / 1. Nominalism / b. Nominalism about universals
The particular/universal distinction is unhelpful clutter; we should accept 'a is F' as basic [Devitt]
     Full Idea: Talk of 'particulars' and 'universals' clutters the landscape without adding to our understanding. We should rest with the basic fact that a is F.
     From: Michael Devitt ('Ostrich Nominalism' or 'Mirage Realism'? [1980], p.98)
     A reaction: Ramsey was first to challenge the basic distinction. I find the approach of Quine and Devitt unsatisfactory. We abandon explanation when it is totally hopeless, but that is usually in the face of complexity. Properties are difficult but simple.
8. Modes of Existence / E. Nominalism / 1. Nominalism / c. Nominalism about abstracta
Quineans take predication about objects as basic, not reference to properties they may have [Devitt]
     Full Idea: For 'a and b have the same property, F-ness' the Quinean Nominalist has a paraphrase to hand: 'a and b are both F'. ..In denying that this object need have properties, the Quinean is not denying that it really is F.
     From: Michael Devitt ('Ostrich Nominalism' or 'Mirage Realism'? [1980], p.95)
     A reaction: The question that remains is why 'F' is used of both a and b. We don't call a and b 'a', because they are different. Quine falls back on resemblance. I suspect Quineans of hiding behind the semantics.
8. Modes of Existence / E. Nominalism / 2. Resemblance Nominalism
Unlike Class Nominalism, Resemblance Nominalism can distinguish natural from unnatural classes [Moreland]
     Full Idea: Resemblance Nominalism is clearly superior to Class Nominalism, since the former offers a clear ground for distinguishing between natural and unnatural classes.
     From: J.P. Moreland (Universals [2001], Ch.2)
     A reaction: Important. It seems evident to me that there are natural classes, and the only ground for this claim would be either the resemblance or the identity of properties.
8. Modes of Existence / E. Nominalism / 3. Predicate Nominalism
There can be predicates with no property, and there are properties with no predicate [Moreland]
     Full Idea: Linguistic predicates are neither sufficient nor necessary for specifying a property. Predicates can be contrived which express no property, properties are far more numerous than linguistic predicates, and properties are what make predicates apply.
     From: J.P. Moreland (Universals [2001], Ch.2)
     A reaction: This seems to me conclusive, and is a crucial argument against anyone who thinks that our metaphysics can simply be inferred from our language.
8. Modes of Existence / E. Nominalism / 5. Class Nominalism
We should abandon the concept of a property since (unlike sets) their identity conditions are unclear [Moreland]
     Full Idea: Some argue that compared to sets, the identity conditions for properties are obscure, and so properties, including realist depictions of them, should be rejected.
     From: J.P. Moreland (Universals [2001], Ch.6)
     A reaction: I have never thought that difficulty in precisely identifying something was a good reason for denying its existence. Consider low morale in a work force. 2nd thoughts: I like this!
9. Objects / D. Essence of Objects / 5. Essence as Kind
Essential kinds may be too specific to provide ontological categories [Westerhoff]
     Full Idea: Essential kinds can be very specific, and arguably too specific for the purposes of ontological categories.
     From: Jan Westerhoff (Ontological Categories [2005], §27)
     A reaction: Interesting. There doesn't seem to be any precise guideline as to how specific an essential kind might be. In scientific essentialism, each of the isotopes of tin has a distinct essence, but why should they not be categories
9. Objects / D. Essence of Objects / 10. Essence as Species
Essentialism concerns the nature of a group, not its category [Devitt]
     Full Idea: Essentialism is concerned with the nature of a group, whatever the category it falls under.
     From: Michael Devitt (Resurrecting Biological Essentialism [2008], 6)
     A reaction: This seems to me such a simple and obvious point that I am amazed that anyone rejects it, yet lots of people seem to think that an essence is just some sort of category.
Things that gradually change, like species, can still have essences [Devitt]
     Full Idea: An intrinsic essence does not have to be 'neat and tidy'. ...Essentialism can accept the gradual change of one thing into another.
     From: Michael Devitt (Resurrecting Biological Essentialism [2008], 11)
     A reaction: My thesis is that essentialism is a response to the needs of explanation, so as long as there is some core explanation to be found, even in something transitory, then the concept of an essence can apply to it.
9. Objects / F. Identity among Objects / 7. Indiscernible Objects
Most philosophers think that the identity of indiscernibles is false [Moreland]
     Full Idea: Most philosophers think that the identity of indiscernibles is false.
     From: J.P. Moreland (Universals [2001], Ch.7)
     A reaction: This is as opposed to the generally accepted 'indiscernibility of identicals'. 'Discernment' is an epistemological concept, and 'identity' is an ontological concept.
12. Knowledge Sources / A. A Priori Knowledge / 4. A Priori as Necessities
Why should necessities only be knowable a priori? That Hesperus is Phosporus is known empirically [Devitt]
     Full Idea: Why should we accept that necessities can only be known a priori? Prima facie, some necessities are known empirically; for example, that water is necessarily H2O, and that Hesperus is necessarily Phosphorus.
     From: Michael Devitt (There is no a Priori [2005], §2)
     A reaction: An important question, whatever your view. If the only thing we can know a priori is necessities, it doesn't follow that necessities can only be known a priori. It gets interesting if we say that some necessities can never be known a priori.
How could the mind have a link to the necessary character of reality? [Devitt]
     Full Idea: What non-experiential link to reality could support insights into its necessary character?
     From: Michael Devitt (There is No A Priori (and reply) [2005], 4)
     A reaction: The key to it, I think, is your theory of mind. If you are a substance dualist, then connecting to such deep things looks fine, but if you are a reductive physicalist then it looks absurdly hopeful.
12. Knowledge Sources / A. A Priori Knowledge / 9. A Priori from Concepts
We explain away a priori knowledge, not as directly empirical, but as indirectly holistically empirical [Devitt]
     Full Idea: We have no need to turn to an a priori explanation of our knowledge of mathematics and logic. Our intuitions that this knowledge is not justified in some direct empirical way is preserved. It is justified in an indirect holistic way.
     From: Michael Devitt (There is no a Priori [2005], §2)
     A reaction: I think this is roughly the right story, but the only way it will work is if we have some sort of theory of abstraction, which gets us up the ladder of generalisations to the ones which, it appears, are necessarily true.
12. Knowledge Sources / A. A Priori Knowledge / 11. Denying the A Priori
The idea of the a priori is so obscure that it won't explain anything [Devitt]
     Full Idea: The whole idea of the a priori is too obscure for it to feature in a good explanation of our knowledge of anything.
     From: Michael Devitt (There is no a Priori [2005], §3)
     A reaction: I never like this style of argument. It would be nice if all the components of all our our explanations were crystal clear. Total clarity about anything is probably a hopeless dream, and we may have to settle for murky corners in all explanations.
Some knowledge must be empirical; naturalism implies that all knowledge is like that [Devitt]
     Full Idea: It is overwhelmingly plausible that some knowledge is empirical. The attractive thesis of naturalism is that all knowledge is; there is only one way of knowing.
     From: Michael Devitt (There is No A Priori (and reply) [2005], 1)
     A reaction: How many ways for us to know seems to depend on what faculties we have. We lump our senses together under a single heading. The arrival of data is not the same as the arrival of knowledge. I'm unconvinced that naturalists like me must accept this.
15. Nature of Minds / C. Capacities of Minds / 3. Abstraction by mind
Abstractions are formed by the mind when it concentrates on some, but not all, the features of a thing [Moreland]
     Full Idea: If something is 'abstract' it is got before the mind by an act of abstraction, that is, by concentrating attention on some (but not all) of what is presented.
     From: J.P. Moreland (Universals [2001], Ch.3)
     A reaction: Presumably it usually involves picking out the behavioural or causal features, and leaving out the physical features - though I suppose it works for physical properties too…
18. Thought / D. Concepts / 4. Structure of Concepts / b. Analysis of concepts
It is always open to a philosopher to claim that some entity or other is unanalysable [Moreland]
     Full Idea: It is always open to a philosopher to claim that some entity or other is unanalysable.
     From: J.P. Moreland (Universals [2001], Ch.2)
     A reaction: For example, Davidson on truth. There is an onus to demonstrate why all attempted analyses fail.
26. Natural Theory / B. Natural Kinds / 1. Natural Kinds
Some kinds are very explanatory, but others less so, and some not at all [Devitt]
     Full Idea: Explanatory significance, hence naturalness, comes in degrees: positing some kinds may be very explanatory, positing others, only a little bit explanatory, positing others still, not explanatory at all.
     From: Michael Devitt (Natural Kinds and Biological Realism [2009], 4)
     A reaction: He mentions 'cousin' as a natural kind that is not very explanatory of anything. It interests us as humans, but not at all in other animals, it seems. ...Nice thought, though, that two squirrels might be cousins...
27. Natural Reality / D. Time / 1. Nature of Time / h. Presentism
'Presentism' is the view that only the present moment exists [Moreland]
     Full Idea: 'Presentism' is the view that only the present moment exists.
     From: J.P. Moreland (Universals [2001], Ch.6)
     A reaction: And Greek scepticism doubted even the present, since there is no space between past and future. It is a delightfully vertigo-inducing idea.
27. Natural Reality / G. Biology / 5. Species
We name species as small to share properties, but large enough to yield generalisations [Devitt]
     Full Idea: Our explanatory purposes in introducing a name for a species demand that we draw the lines around a group that is small enough to share a whole lot of important properties and large enough to yield broad generalizations.
     From: Michael Devitt (Resurrecting Biological Essentialism [2008], 10 'Arb')
     A reaction: Grist to my mill. In this reaction slot (16th Oct 2013) I launch my new metaphysical school - welcome to EXPLANATIONISM! Folk metaphysics, and the best philosophical metaphysics, is entirely driven by the needs of explanation.
Species are phenetic, biological, niche, or phylogenetic-cladistic [Devitt, by PG]
     Full Idea: The four main concepts of a species are 'phenetic' (similarity of traits), 'biological species' (interbreeding and isolated), 'ecological niche' (occupying an adaptive zone), or 'phylogenetic-cladistic' (start and finish at splits in lineage)
     From: report of Michael Devitt (Resurrecting Biological Essentialism [2008], 4) by PG - Db (ideas)
     A reaction: [my summary of Devitt's list] Devitt attacks the whole lot, in favour of essentialism - the species being fixed by its underlying explanatory mechanisms.
The higher categories are not natural kinds, so the Linnaean hierarchy should be given up [Devitt]
     Full Idea: The signs are that the higher categories are not natural kinds and so the Linnaean hierarchy must be abandoned. ...This is not abandoning a hierarchy altogether, it is not abandoning a tree of life.
     From: Michael Devitt (Natural Kinds and Biological Realism [2009], 6)
     A reaction: Devitt's underlying point is that the higher and more general kinds do not have an essence (a specific nature), which is the qualification to be a natural kind. They explain nothing. Essence is the hallmark of natural kinds. Hmmm.
Species pluralism says there are several good accounts of what a species is [Devitt]
     Full Idea: Species pluralism is the view that there are several equally good accounts of what it is to be a species.
     From: Michael Devitt (Natural Kinds and Biological Realism [2009], 7)
     A reaction: Devitt votes for it, and cites Dupré, among many other. Given the existence of rival accounts, all making good points, it is hard to resist this view.