Q: I was doing Ex. 1.3 and I can't figure out how to make a = d in Taski's World. What is a = d?

A: It is the '=' of math! It says that 'a is d', in just the same way '2+2 = 4' says '2+2 is 4'. Or another example, 'Nick = Prof Huggett' says 'Nick is Prof Huggett'. That is, there aren't two things, a and d, or 2+2 and 4, or Nick and Prof Huggett, in each case there is only one thing, under two different names. = is called 'identity', and it says that the two names name the very same thing. It is therefore not (merely) to say that a and d have all the same properties in common.

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