Do animals pretend?

This is my first foray into Sunday cat blogging. Here goes.

Many philosophers have spent a fair amount of time thinking about pretense -- what exactly it is, and how to apply a theory of pretense to various areas of philosophical interest (e.g. perhaps we are playing a game of pretend when we talk about the natural numbers).

I was just watching my cat play with a fuzzy cat toy. The cat, in some sense, realizes that the fuzzy ball is not a mouse (or whatever). However, when it is playing with the toy, it will temporarily exhibit many of the behaviors that it would exhibit toward a real mouse -- e.g., it hides behind furniture so that the toy won't 'see' it.

All the philosophical discussions of pretense with which I am familiar are restricted to human pretense. But given the kinds of things I see with my cat, and given that pretense occurs fairly early in childhood development (sophisticated multi-person pretend games start around 3 1/2), it seems at least possible that animals engage in pretense too.

And if my cat isn't engaged in a pretense, then what exactly is it doing?

New philosophy of physics blog

I somehow missed this: there's a new philosophy of physics blog by my erstwhile office-mate Chris Wüthrich, who's now at UCSD. It's cleverly titled "Taking up Spacetime," and it looks promising -- he has a good recent post up about the notion of structure.

logic teaching question

I'm teaching Symbolic Logic this term, and we just introduced the notion that two syntactically distinct sentences can mean exactly the same thing (e.g. DeMorgan's Laws). In class yesterday, I asked the students to come up with a criterion for when two sentences are identical in meaning. We eventually reached the "official" answer: S_1 and S_2 are synonymous just in case they have the same truth-value in all models (ok, we're not using the notion of models; for us, it's "... in all possible arrangements of the board" in Tarski's World -- we're using Barwise and Etchemendy's Language, Proof, and Logic.)

Along the way to the official answer, though, a student gave the following characterization:

Sentences S_1 and S_2 are synonymous just in case the set of all sentences that follow from* S_1 is identical to the set of all sentences that follow from S_2.

After class, I jotted down a proof-sketch showing that the student's characterization is equivalent to the "official" one. But I'm not 100% confident in it, so I'm just curious whether anyone can see a counter-example (i.e. are there any 2 sentences that meet one characterization but not the other?).
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* EDIT: As Bryan made me realize in the comments, I should specify that 'follows from' here is semantic, not syntactic/ proof-theoretic; i.e. 'Conclusion C follows from premise P' means that every model (or world, or construction, or whatever it is that makes sentences true in your formal semantics) in which P is true is also a model in which C is true.