3 ideas
| 8920 | Equivalence relations are reflexive, symmetric and transitive, and classify similar objects [Lipschutz] |
| Full Idea: A relation R on a non-empty set S is an equivalence relation if it is reflexive (for each member a, aRa), symmetric (if aRb, then bRa), and transitive (aRb and bRc, so aRc). It tries to classify objects that are in some way 'alike'. | |
| From: Seymour Lipschutz (Set Theory and related topics (2nd ed) [1998], 3.9) | |
| A reaction: So this is an attempt to formalise the common sense notion of seeing that two things have something in common. Presumably a 'way' of being alike is going to be a property or a part |
| 18925 | If talking donkeys are possible, something exists which could be a talking donkey [Williamson, by Cameron] |
| Full Idea: Williamson's view on modality is that everything that could exist does exist: since there could exist a talking donkey there actually exists some thing that could be a talking donkey. | |
| From: report of Timothy Williamson (Modal Logic as Metaphysics [2013], n20) by Ross P. Cameron - Truthmaking for Presentists n20 | |
| A reaction: Well that thing certainly isn't me, or Tim Williamson. I'm guessing that the thing is an actual donkey, probably a rather bright one. Actually, I think this is one of those views that invites the incredulous stare. (Barcan formulae). |
| 3643 | The concept of mind excludes body, and vice versa [Descartes] |
| Full Idea: The concept of body includes nothing at all which belongs to the mind, and the concept of mind includes nothing at all which belongs to the body. | |
| From: René Descartes (Reply to Fourth Objections [1641], 225) | |
| A reaction: A headache? Hunger? The mistake, I think, is to regard the mind as entirely conscious, thus creating a sharp boundary between two aspects of our lives. As shown by blindsight, I take many of my central mental operations to be pre- or non-conscious. |