- Go to philoftime.michaelde.com for course material including slides, readings, questions and answers, etc.
- Evaluation will consist of four small essays of 2000-2500 words each. Hausarbeit is not possible.
- Being a seminar, class participation is very important. Don't be shy! (Or, if you can't help being shy, fight it one question/comment at a time.)
- Weekly readings are crucial, as they form the basis of our meetings/discussions.
- If you have any questions, don't hesitate to contact me. I'm happy to schedule meetings by appointment.
- The philosophy of time enjoys a long and rich history, from the presocratics until today. Some central topics include
- the nature of time (what is it and what are its properties and structure)
- paradoxes (e.g. of time travel, of identity)
- the relation of time to free will, free action, and the open future
- fatalism, determinism
- diachronic identity/identity over time/persistence/change, Leibniz's law
- tense (are such operators primitive, implicit quantifiers over moments, etc.)
Aristotle on fatalism (in De Interpretation 9)
Again, if it is white now it was true to say earlier that it would be white; so that it was always true to say of anything that has happened that it would be so. But if it was always true to say that it was so, or would be so, it could not not be so, or not be going to be so. But if something cannot not happen it is impossible for it not to happen; and if it is impossible for something not to happen it is necessary for it to happen. Everything that will be, therefore, happens necessarily. So nothing will come about as chance has it or by chance; for if by chance, not of necessity. [18 b 9 ft] in [Ackrill, 1963, pp 50-51].
- Either it will rain tomorrow or it won't
- Suppose it will rain. Then it's true now that it will rain, so it's true of necessity.
- Suppose it won't. Then it's true now that it won't, so it's true of necessity.
- Therefore, it's either true of necessity that it will rain, or it's true of necessity that it won't.
Divine foreknowledge and fatalism
- For every proposition p, God knows whether or not p
- In particular, then, God knows whether or not it will rain
- Whatever God knows, he knows of necessity
- So if God knows that it will rain, he knows of necessity that it will rain
- But then if he knows that it will rain, it couldn't have been any other way, and likewise if he knows that it won't rain
- In either case, it couldn't have been any other way
We ought to regard the present state of the universe as the effect of its antecedent state and as the cause of the state that is to follow. An intelligence knowing all the forces acting in nature at a given instant, as well as the momentary positions of all things in the universe, would be able to comprehend in one single formula the motions of the largest bodies as well as the lightest atoms in the world, provided that its intellect were sufficiently powerful to subject all data to analysis; to it nothing would be uncertain, the future as well as the past would be present to its eyes. The perfection that the human mind has been able to give to astronomy affords but a feeble outline of such an intelligence. [Laplace 1820]
A rough formulation of determinism
- The world is deterministic iff, for any times x and y, the propositions true at x, along with the laws of nature, entail the propositions true at y.
- In other worlds, a specification of the way things are any time can be determined from a specification of the way things are at any other time, together with the laws of nature.
- Determinism therefore implies fatalism: if things were a certain way then, given the laws of nature, they now couldn't be (and couldn't have been) otherwise.
- The only sense in which things could have been otherwise is if the laws of nature or the initial conditions (if there be) could have been different.
- This has implications for theories of free action and free will. If the universe is deterministic, can we have free will and can any of our actions be free?
A puzzle about persistence
- Let us say that a thing persists if it exists at more than one time while undergoing change.
- Leibniz's Law (LL) states that two things are identical iff they share all their properties.
- Now here is a puzzle about persistence:
- Call the person at time x with long hair, Longhair. (Say me a long time ago.)
- Call the person at time y with short hair, Shorthair. (Say me today.)
- Longhair has long hair, and Shorthair does not.
- By LL, Longhair is not identical to Shorthair.
- By an obvious generalization, nothing persists.
Some solutions, in brief
- Deny Leibniz's Law. Perhaps reformulate it, e.g. to: two things are identical at a time x iff, at x, they share all their properties.
- The property of having short/long hair is actually a relation to a time: s has long hair at time x. Then the having of short hair at x and the having of long hair at y are not incompatible properties.
- Instantiation (the property of having?) is relational: s has-at-x long hair. Then having-at-x long hair and having-at-y short hair are not incompatible.
- Deny that there are any tensed truths outside of those concerning the present. Then only 'x has short hair' is true, and 'x had long hair' is not.
- Deny that it makes sense to name a thing-at-a-time. What exactly are 'Longhair' and 'Shorthair' referring to? If me, then it's false that Longhair has long hair.
For next week, please read
- Ned Markosian, Time, The Stanford Encylopedia of Philosophy
- Weekly questions (to be used as a guide for the following week's discussion) are available on the site. Answers follow the next week by going back to the question page.