They mean different things: http://french.about.com/od/grammar/a/savoirconnaitre.htm

Whether one thinks there is overwhelming evidence in opposition of solipsism may depend on what one takes evidence to be. Arguably, if evidence is just the way things seem, construed in the most minimal, least question-begging way possible, then there is no evidence in opposition to sopipsism at all. Things might seem just this way, and yet there be nothing in the universe other than my own experiences. Why suppose that in addition to those experiences, those things of which one does have knowledge, there is some other stuff about which one has no knowledge at all? It seems hard even to form a conception of what such other stuff might be like, since conceptions seem to be formed from the material of experience itself and unsuited to picture for us this myserious others stuff of which we know nothing. Personally I don't buy into that sort of soplispistic reasoning. But I expect that a solipsistic worldview could be made consistent with the beliefs one needs to live a normal life. The loaf of...

" I recognize that there is some not inconsiderable paradox in doubting the very idea of being able to form a thought and using thought to achieve that doubt". Well spotted! Suppose that your doubts about memory lead you this: "I cannot trust any thought, including this one". Where do you go from there? It doesn't look as though the paradoxical nature the thought undermines it in such a way that you can conclude that it is false, and proceed to trust some thoughts. It sort of leaves you with nowhere to go. I agree with Stephen. Memory is not that unreliable. It is much less reliable than we think. When we seem to remember things our brains seem to do a lot of construction and interpretation, and present to us a partly made-up image of some past even as if it were a perfectly accurate representation. This can get us into trouble. But our short-term memory is pretty good and serves its purpose. It is not hard to keep track of the thoughts involved in a short line of reasoning. It also gets a...

I take it that thenature/nurture controversy is the controversy concerning how much of ourcognition is innate, rather than acquired. One thing that philosophers havetried to do is get clear about what ‘innate’ might mean in this context. ‘Innate’ is not a term that is used incontemporary biology. The first idea that pops to mind is that a trait isinnate if an only if it is present at birth. But this won’t do because prenatallearning is possible. And some apparently innate characteristics, such as facialhair, appear only after birth. Thus presence at birth is neither sufficient nornecessary for innateness. Terms like ‘genetically determined’ and ‘geneticallyspecified’ won’t do either. No trait is 100% genetically determined, since theenvironment always has a causal role to play in development. And ‘geneticallyspecified’ is just a metaphor: genes do not in any literal sense specifyphenotypic traits. (For discussion, see Richard Samuels (2004) "Innateness and CognitiveScience", Trends in Cognitive...