Today we were introduced to David Hume. Hume distinguishes impressions from ideas: both are mental phenomena, but impressions are more vivid and forceful. When you see a cat, the seen cat is an impression. When you get angry, the anger is an impression. The memory of these things is an idea.
Hume's version of Empiricism is captured in his copy principle. The copy principle states that: Every idea is a copy of an impression. As we will see, Hume uses this principle as a weapon against his philosophical enemies.
However, Hume also allows for a very puzzling exception to the copy principle. Every distinct shade of colour is a different idea, Hume insists, and the copy principle applies. You can't just imagine new ideas of colour, you have to get impressions of them through experience - otherwise if you saw one colour, you could learn all the other colours by changing the colour very slightly again and again, without experience. And yet - even though this seems to contract what I have just written, Hume also thinks that someone familiar with pretty much every shade of blue but missing just one shade could generate an idea of it without an impression! Hume allows there will be a few other such cases, but in general he's not very worried about them.
We briefly mentioned the philosophy action figures. Unfortunately these have gotten a bit harder to find. You can check out the whole set here.