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 / D. Definition / 5. Genus and Differentia
If definitions must be general, and general terms can't individuate, then Socrates can't be defined
The definitions expressing identity are used to sort things
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
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 / 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
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
Aristotelian essence underlies behaviour, or underlies definition, or is the source of existence
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
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 / j. 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
The mind abstracts generalities from images, but also uses images for understanding
Very general ideas (being, oneness, potentiality) can be abstracted from thought matter in general
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 / 1. Free Will / a. Nature of free will
If we saw something as totally and utterly good, we would be compelled to will it
16. Persons / F. Free Will / 1. Free Will / b. Pro-free will
The will is not compelled to move, even if pleasant things are set before it
Because the will moves by examining alternatives, it doesn't compel itself to will
Nothing can be willed except what is good, but good is very varied, and so choices are unpredictable
However habituated you are, given time to ponder you can go against a habit
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 / 1. Free Will / c. Free will critique
We must admit that when the will is not willing something, the first movement to will must come from outside the will
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 / B. 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
The will must aim at happiness, but can choose the means
We don't have to will even perfect good, because we can choose not to think of it
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
24. Applied Ethics / C. Death Issues / 3. Abortion
Aquinas says a fertilized egg is not human, and has no immortal soul
25. Society / E. State Functions / 6. War
For Aquinas a war must be in a just cause, have proper authority, and aim at good
26. Natural Theory / B. Concepts of Nature / 4. Time / a. Time
Eternity coexists with passing time, as the centre of a circle coexists with its circumference
26. Natural Theory / C. Causation / 1. Causation / e. Direction of causation
A cause can exist without its effect, but the effect cannot exist without its cause
26. Natural Theory / C. Causation / 3. General Causation / d. Causal necessity
Even a sufficient cause doesn't compel its effect, because interference could interrupt the process
27. Natural Reality / A. Physics / 1. Matter / g. Matter as extension
Bodies are three-dimensional substances
28. God / C. Proofs of Reason / 2. Ontological Proof critique
God's existence may be self-evident in itself, but it is not self-evident to limited human beings
The fool in Psalm 52 seems to conceive of God's non-existence, so His existence can't be self-evident
28. God / C. Proofs of Reason / 3. Moral Argument
Fourth Way: qualities with gradations (like goodness) depend on a maximum for that quality, so there is a supreme being
28. God / D. Proofs of Evidence / 1. Cosmological Proof
Second Way: everything has a cause, and this can't go back to infinity, so there is a First Cause
Third Way: if everything was contingent it would all have vanished by now, and it hasn't, so something must be necessary
If you assume that there must be a necessary being, you can't say which being has this quality
First Way: movement is impossible without a First Mover
If nature and human will explain everything that happens, only God can explain those things
28. God / D. Proofs of Evidence / 2. Teleological Proof
Fifth Way: everything acts ignorantly to some end, so an intelligence must provide the end
29. Religion / C. Monotheistic Religion / 3. Christianity / a. Christianity
Life aims at the Beatific Vision - of perfect happiness, and revealed truth
29. Religion / C. Monotheistic Religion / 3. Christianity / d. Heresy
Heretics should be eradicated like wolves
29. Religion / E. Immortality / 1. Immortality
If the soul achieves well-being in another life, it doesn't follow that I do
29. Religion / E. Immortality / 4. Heaven
Those in bliss have their happiness increased by seeing the damned punished
29. Religion / F. Problem of Evil / 1. Problem of Evil
Evil must be tolerated, because it allows God to bring good out of evil, which is a supreme good