Locke's External World

One of Locke's main points is obviously that we only know things through experience. So, you can only know what a chair is if you have experienced a chair in the external world (or, perhaps, you perceived all the parts of the chair in the external world and thereby inferred what a chair is). What I'm interested in here is that Locke kind of just assumes that the external world exists, rather than making an argument for it. Descartes dabbled in the question, so I was surprised to find that Locke did not pay much attention to it. Certainly, according to Locke, since we do not have any innate ideas, we cannot just know that the external world exists. So, at one point, Locke talks about how it has to be true that the external world exists because it is the best explanation for the evidence at hand. This is not a solid explanation, but rather an assumption that fits nicely into his other arguments. Although I am not one to doubt the existence of the external world, I find it interesting that Locke didn't tackle the issue wholeheartedly.