 Another way to meet at least some of these challenges to an empiricist account of the origin of our concepts is to revise our understanding of the content of our concepts so as to bring them more in line with what experience will clearly provide. Hume famously takes this approach. Beginning in a way reminiscent of Locke, he distinguishes between two forms of mental contents or “perceptions,” as he calls them: impressions and ideas. Impressions are the contents of our current experiences: our sensations, feelings, emotions, desires, and so on. Ideas are mental contents derived from impressions. Simple ideas are copies of impressions; complex ideas are derived from impressions by “compounding, transposing, augmenting or diminishing” them. Given that all our ideas are thus gained from experience, Hume offers us the following method for determining the content of any idea and thereby the meaning of any term taken to express it.