Ideas of Thomas Aquinas, by Theme

[Italian, 1225 - 1274, Born Roccasecca, Italy. Dominican monk. Taught by Albertus Magnus. Based Paris, then Italy. Died at Fossanova. 'Doctor Angelicus'.]

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2. Reason / A. Nature of Reason / 1. On Reason
We are coerced into assent to a truth by reason's violence
2. Reason / A. Nature of Reason / 4. Aims of Reason
The mind is compelled by necessary truths, but not by contingent truths
2. Reason / B. Laws of Thought / 6. Ockham's Razor
Supposing many principles is superfluous if a few will do it
2. Reason / D. Definition / 5. Genus and Differentia
If definitions must be general, and general terms can't individuate, then Socrates can't be defined [Cover/O'Leary-Hawthorne]
The definitions expressing identity are used to sort things
3. Truth / A. Truth Problems / 1. Truth
Speak lies, intend lies, intend deception, aim at deceptive goal? [Tuckness/Wolf]
3. Truth / A. Truth Problems / 3. Value of Truth
For the mind Good is one truth among many, and Truth is one good among many
3. Truth / A. Truth Problems / 9. Rejecting Truth
If the existence of truth is denied, the 'Truth does not exist' must be true!
7. Existence / A. Nature of Existence / 3. Being / e. Being and nothing
If affirmative propositions express being, we affirm about what is absent
7. Existence / A. Nature of Existence / 3. Being / g. Particular being
Being implies distinctness, which implies division, unity, and multitude
7. Existence / D. Theories of Reality / 4. Naturalism
Non-human things are explicable naturally, and voluntary things by the will, so God is not needed
7. Existence / E. Categories / 4. Category Realism
Different genera are delimited by modes of predication, which rest on modes of being
8. Modes of Existence / B. Properties / 8. Properties as Modes
Whiteness does not exist, but by it something can exist-as-white
Properties have an incomplete essence, with definitions referring to their subject
8. Modes of Existence / D. Universals / 6. Platonic Forms / d. Forms critiques
If the form of 'human' contains 'many', Socrates isn't human; if it contains 'one', Socrates is Plato
9. Objects / A. Existence of Objects / 4. Individuation / a. Individuation
The principle of diversity for corporeal substances is their matter [Cover/O'Leary-Hawthorne]
9. Objects / B. Unity of Objects / 1. Unifying an Object / b. Unifying aggregates
'One' can mean undivided and not a multitude, or it can add measurement, giving number
9. Objects / C. Structure of Objects / 2. Hylomorphism / d. Form as unifier
Humans only have a single substantial form, which contains the others and acts for them
One thing needs a single thing to unite it; if there were two forms, something must unite them
9. Objects / D. Essence of Objects / 1. Essences of Objects
It is by having essence that things exist
9. Objects / D. Essence of Objects / 2. Types of Essence
Specific individual essence is defined by material, and generic essence is defined by form
9. Objects / D. Essence of Objects / 4. Essence as Definition
The definition of a physical object must include the material as well as the form
9. Objects / D. Essence of Objects / 5. Essence as Kind
Essence is something in common between the natures which sort things into categories
9. Objects / D. Essence of Objects / 6. Essence as Unifier
A simple substance is its own essence
11. Knowledge Aims / C. Knowing Reality / 1. Perceptual Realism / b. Direct realism
A knowing being possesses a further reality, the 'presence' of the thing known
12. Knowledge Sources / A. A Priori Knowledge / 2. Self-Evidence
Some things are self-evident to us; others are only self-evident in themselves
12. Knowledge Sources / A. A Priori Knowledge / 8. A Priori as Analytic
A proposition is self-evident if the predicate is included in the essence of the subject
12. Knowledge Sources / C. Rationalism / 1. Rationalism
Sensation prepares the way for intellectual knowledge, which needs the virtues of reason
12. Knowledge Sources / D. Empiricism / 5. Empiricism Critique
Knowledge may be based on senses, but we needn't sense all our knowledge
14. Science / D. Explanation / 2. Types of Explanation / k. Explanations by essence
Definition of essence makes things understandable
15. Nature of Minds / C. Capacities of Minds / 2. Imagination
Mental activity combines what we sense with imagination of what is not present
15. Nature of Minds / C. Capacities of Minds / 3. Abstraction by mind
Abstracting A from B generates truth, as long as the connection is not denied
15. Nature of Minds / C. Capacities of Minds / 5. Generalisation by mind
We understand the general nature of things by ignoring individual peculiarities
Very general ideas (being, oneness, potentiality) can be abstracted from thought matter in general
The mind abstracts generalities from images, but also uses images for understanding
Particular instances come first, and (pace Plato) generalisations are abstracted from them
Species are abstracted from appearances by ignoring individual conditions
16. Persons / F. Free Will / 3. Constraints on the will
If we saw something as totally and utterly good, we would be compelled to will it
16. Persons / F. Free Will / 4. For Free Will
Nothing can be willed except what is good, but good is very varied, and so choices are unpredictable
The will is not compelled to move, even if pleasant things are set before it
However habituated you are, given time to ponder you can go against a habit
Because the will moves by examining alternatives, it doesn't compel itself to will
Since will is a reasoning power, it can entertain opposites, so it is not compelled to embrace one of them
16. Persons / F. Free Will / 5. Against Free Will
We must admit that when the will is not willing something, the first movement to will must come from outside the will
17. Mind and Body / A. Mind-Body Dualism / 4. Occasionalism
Without God's influence every operation would stop, so God causes everything
18. Thought / E. Abstraction / 1. Abstract Thought
We abstract forms from appearances, and acquire knowledge of immaterial things
Understanding consists entirely of grasping abstracted species
18. Thought / E. Abstraction / 2. Abstracta by Selection
Mathematics can be abstracted from sensible matter, and from individual intelligible matter
18. Thought / E. Abstraction / 3. Abstracta by Ignoring
Mathematical objects abstract both from perceived matter, and from particular substance
We can just think of an apple's colour, because the apple is not part of the colour's nature
Abstracting either treats something as separate, or thinks of it separately
Numbers and shapes are abstracted by ignoring their sensible qualities
18. Thought / E. Abstraction / 8. Abstractionism Critique
The mind must produce by its own power an image of the individual species
19. Language / C. Assigning Meanings / 3. Predicates
The mind constructs complete attributions, based on the unified elements of the real world
20. Action / B. Preliminaries of Action / 2. Willed Action / a. Will to Act
The will can only want what it thinks is good
We don't have to will even perfect good, because we can choose not to think of it
The will must aim at happiness, but can choose the means
22. Metaethics / B. The Good / 1. Goodness / g. Consequentialism
Good applies to goals, just as truth applies to ideas in the mind
22. Metaethics / C. Ethics Foundations / 1. Nature of Ethics / g. Moral responsibility
Without free will not only is ethical action meaningless, but also planning, commanding, praising and blaming
23. Ethics / C. Virtue Theory / 2. Elements of Virtue Theory / d. Teaching virtue
Aquinas wanted, not to escape desire, but to transform it for moral ends [MacIntyre]
24. Applied Ethics / C. Death Issues / 3. Abortion
Aquinas says a fertilized egg is not human, and has no immortal soul [Martin/Barresi]
25. Society / E. State Functions / 5. War
For Aquinas a war must be in a just cause, have proper authority, and aim at good [Grayling]
26. Natural Theory / A. Speculations on Nature / 7. Later Matter Theories / c. Matter as extension
Bodies are three-dimensional substances
26. Natural Theory / C. Causation / 5. Direction of causation
A cause can exist without its effect, but the effect cannot exist without its cause
26. Natural Theory / C. Causation / 9. General Causation / d. Causal necessity
Even a sufficient cause doesn't compel its effect, because interference could interrupt the process
27. Natural Reality / C. Space-Time / 2. Time / a. Time
Eternity coexists with passing time, as the centre of a circle coexists with its circumference
28. God / B. Proving God / 2. Proofs of Reason / b. Ontological Proof critique
We can't know God's essence, so his existence can't be self-evident for us
28. God / B. Proving God / 3. Proofs of Evidence / a. Cosmological Proof
Way 1: the infinite chain of potential-to-actual movement has to have a first mover
Way 3: contingent beings eventually vanish, so continuity needs a necessary being
Way 2: no effect without a cause, and this cannot go back to infinity, so there is First Cause
Way 4: the source of al qualities is their maximum, so something (God) causes all perfections
If you assume that there must be a necessary being, you can't say which being has this quality [Kant]
28. God / B. Proving God / 3. Proofs of Evidence / b. Teleological Proof
Way 5: mindless things act towards an obvious end, so there is an intelligent director
29. Religion / B. Monotheistic Religion / 4. Christianity / a. Christianity
Life aims at the Beatific Vision - of perfect happiness, and revealed truth [Zagzebski]
29. Religion / B. Monotheistic Religion / 4. Christianity / d. Heresy
Heretics should be eradicated like wolves
29. Religion / D. Religious Issues / 2. Immortality / a. Immortality
If the soul achieves well-being in another life, it doesn't follow that I do
29. Religion / D. Religious Issues / 2. Immortality / d. Heaven
Those in bliss have their happiness increased by seeing the damned punished
29. Religion / D. Religious Issues / 3. Problem of Evil / a. Problem of Evil
God does not exist, because He is infinite and good, and so no evil should be discoverable
It is part of God's supreme goodness that He brings good even out of evil