Week 4: Kinds of Truth - Necessity

Question 1

Deontic, Epistemic and Alethic modalities

Answer 1

Deontic modality is compatible with obligations (e.g., permission), Epistemic modality is compatible with what we know (e.g., knowledge), and Alethic modality is compatible with certain aspects of reality (e.g., ability).

Question 2

Physical and metaphysical possibility

Answer 2

Physical possibility refers to what is possible given the laws of nature, while metaphysical possibility (or absolute possibility) refers to what could be the case in the broadest sense (e.g., nothing can be both a dog and not a dog).

Question 3

Possible and actual worlds

Answer 3

A possible world is a way reality could be (e.g., one where I am a midget), consistent (no impossibilities/logical contradictions), and maximal (fully specific). The actual world is the way reality actually is (e.g., I am not a midget).

Question 4

Duality

Answer 4

Duality refers to the inter-definability of possibility and necessity (e.g., p is possible iff not-p is not necessary, and vice versa).

Question 5

Truth

Answer 5

What is necessarily true is true, and what is true is possibly true. Necessity entails possibility.

Question 6

Contingency

Answer 6

Contingent refers to something that is both possibly true and possibly false (i.e., possible that p and possible that not p).

Question 7

Contingent truth

Answer 7

A contingent truth is a statement that is true and contingent.

Question 8

Metaphysical and physical necessity

Answer 8

Metaphysical necessity refers to what has to be the case in the broadest sense, true at all possible worlds, while physical necessity is true at all possible worlds that obey the laws of physics.

Question 9

Metaphysical necessities supposed to be analytic, a priori

Answer 9

Analytic a priori metaphysical necessities include logical truths (e.g., there are elephants or there are no elephants), mathematical truths (e.g., there are infinitely many prime numbers), and analytic truths (e.g., somebody who is a bachelor is unmarried).

Question 10

Metaphysical necessities supposed to be synthetic, a posteriori

Answer 10

Synthetic a posteriori metaphysical necessities include identity claims about individuals and natural kinds (when true), claims that are true ‘in virtue of the nature of things,’ essence of individuals, claims of constitution, and claims of origin.

Question 11

Truths not supposed to be necessary

Answer 11

Non-necessary truths include ordinary contingent truths, laws of nature that do not result from the nature of things, Kripke’s contingent a priori claims (e.g., The International Prototype Kilogram in Paris has a mass of 1 kg), contingent a priori claims involving indexicals (e.g., I am here now), Evans’ contingent a priori claims involving stipulative definitions (e.g., Using “Julius” as a name for whomever actually invented the zip—if there is indeed a unique inventor), and contingent synthetic claims based on empirical evidence (e.g., The Earth revolves around the Sun).