Counterfactuals

Is there a difference between the following statements:

  1. If a kangaroo had no tail then it would fall over.
  2. If the gravitational constant were different then humans would not exist.
  3. If you were a woman then you would have a different philosophy.

The Wednesday philosophy meetup was sparsely attended, only 4 of us, and a bit thick to get through, but still interesting. Our topic was counterfactuals. Harland proposed the topic because he wanted to find a logical response to (3), an argument that he wants to reject. So he walked us through a chunk of Nelson Goodman and David Lewis. There was a lot of technical tooing-and-froing about the set of conditions that would invalidate a counterfactual statement and possible worlds a la Lewis that were close enough to our world to only be different in respect to the antecedent. We concluded that it was a difficult topic and a good effort by all present.

The nagging questions still bugging me is whether we can really treat all of sentences the same way. The balancing ability of a kangaroo seems quite different from the philosophic prowess of a woman or man. Should logic treat them the same way?

Furthermore, I wonder just what is the purpose of our making counterfactual statements. I think one reason we use these statements is to teach others about our point of view or beliefs. Saying that a kangaroo would fall over without a tail is just a way of saying that tails are an important part of how a kangaroo keeps its balance. Making a statement like (3) is a way of saying that your philosophy depends on your gender. I feel there is something in the purpose of these statements that might help to unlock them but it remains just beyond my grasp.