Could I have been my sister? Thanks, Bob.

But perhaps the question is not whether the two of us could have existed as one, but whether I could have been her. It’s certainly easy to imagine oneself as another person (well, perhaps not so easy), and this sympathetic imagination easily leads to the question whether I could have actually been the person whose experiences I’m imagining? Could I have been Napolean? If my mother had waited just a few minutes before having sex with my father, would I have been a different person (since undoubtedly a different sperm and egg would have united)? If my mother had had sex with a different man, would I have been an even more different person?

Some years ago I heard one of the Beatles in the course of a conversation about his career opine that 'after all I might easily have been someone else, mightn't I'. I remember not being sure about this proposition. One half knows what is being got at but on the other hand, it seems barely intelligible. Could I easily have been someone else? Ian g

Several years ago, in a fit of anger at her father, my daughter turned her anger on me and demanded that I explain to her why I had ever gotten involved with him. I pointed out to her that she had no right to be angry at me on these grounds, since she wouldn’t have existed had it not been for my involvement with him. Her origins are essential to her, and she wouldn’t have existed had it not been for these origins. Might she then have reasonably replied that she could have been someone else? I agree that this claim is barely coherent. It is true that she could have had many different attributes. She might not have developed certain interests; she might not have looked exactly the way that she looks. But that’s not to say that she could have been someone else; it’s to say that she– the very same person– could have had certain different attributes. For further thoughts that are relevant to this question, see 302 and 433 .

How do formal logicians respond to Marxist/Leninist/Dialectical logic claims? For example, in "An Introduction to the Logic of Marxism", George Novack explains that the law of identity of formal logic, that "A is equal to A", is always falsified when we try to apply it to reality. Here is a quote from the book, in which he quotes from "In Defense of Marxism" (it is long, I apologize): "... a pound of sugar is equal to itself. Neither is this true -- all bodies change uninterruptedly in size, weight, color, etc. They are never equal to themselves. A sophist will respond that a pound of sugar is equal to itself at 'any given moment.' "Aside from the extremely dubious practical value of this 'axiom,' it does not withstand theoretical criticism either. How should we really conceive the word 'moment'? If it is an infinitesimal interval of time, then a pound of sugar is subjected during the course of that 'moment' to inevitable changes. Or is the 'moment' a purely mathematical abstraction, that is, a...

According to a standard conception of identity, if A is identical to B , then A and B haveall of their properties in common. This principle is commonly known asLeibniz’s law, after the philosopher Gottfried Wilhelm Leibniz, a 17thcentury German philosopher, who articulated this implication of ourconcept of identity. This principle is also referred to as "theprinciple of the indiscernibility of identicals". This law or principlemight seem to imply that if a particular object (say a particularquantity of sugar) changes over time, then it’s not the same thing–after all, the properties of the object at one time are different fromthe properties of that object at another time. However, this reasoningrests on a confusion. Leibniz’s law does not imply that if A at T1 has properties f , g , and h , then A at T2 must have these same properties. Instead, it implies that, if it is true of A that at T1 it has properties f , g , and h , then at T2 it is true of A that...

I never understood Heraclitus' river analogy. Does it mean that we are constantly changing or changing only by degrees? Why does it say the "same" river if it is in constant flux? It seems like in the fragment "one can never step in the same river twice" that we could interpret the "step" as "never step in the same river" or as "never step into the same waters". Which is correct?

In Plato’s Cratylus , the character Socrates makes thefollowing comment about Heraclitus: “Heraclitus is supposed to say thatall things are in motion and nothing at rest; he compares them to thestream of a river, and says that you cannot go into the same rivertwice" (402a). Ever since Plato, the view that we can’t step twice intothe same river has been attributed to Heraclitus. However,let’s consider the following two fragments about rivers that manyancient scholars regard as Heraclitus’ own words (in translation): "On those who enter the same rivers, ever different waters flow– and souls are exhaled from the moist things" [B 12]. "We step and do not step into the same rivers, we are and we are not" [B 49a]. Inthe first fragment, Heraclitus suggests that we do step into the samerivers, even though the water in these rivers changes. The secondfragment raises interpretative problems of its own, but here tooHeraclitus speaks of the same rivers. So how can we choosebetween...