Locke: Against Descartes & innate ideas

As I spoke about in an earlier post, Locke does not believe in innate ideas. Descartes, on the other hand, loves innate ideas. The cogito rests on that principle, as you don't need any sensation or perception from the outside world in order to think and determine that you therefore exist. Descartes also uses "nature taught me so" as an explanation for various arguments that he tackles (one is what particularly makes humans more intelligent than animals; another is what accounts for the pairing of a particular mind with a particular body). "Nature taught me so" is obviously just another way of saying that he was born with that innate idea.

Locke argues against innate ideas and asserts that neither speculative (logical & metaphysical) nor practical (ethical) principles are known to us at birth. He argues that such principles are not universal among humans. He also claims that if they were universal, then they could easily be explained by way of self-evidence and/or shared experience. Another argument he uses is that children and the mentally handicapped are not familiar with these principles, and nothing could account for their sudden loss and eventual regain (in the case of children) of them. I'm inclined to believe Locke's argument because everything I know seems to come from outside sources--either someone told me, or I learned it by comparing it to something else. So, for example, I know that 2+2=4 because someone taught me how to count and add numbers. I know that I'm kind of short because I've seen a lot of other people who are taller than me.