Now, Descartes's first proof for God's existence does have some initial plausibility. For example, if I discovered my ten-year-old daughter had drawn an apparently accurate diagram of a very sophisticated computer system, I would quickly infer that some mind other than the child's (and one much more informed about computers) had been at work and was, in fact, the source of the idea.
The analogy here seems clear and distinct enough, since obviously the child's mind could not have produced the diagram unaided. So to that extent Descartes's argument that the idea of God's perfection in an imperfect creature must come from a divine source seems fair enough. But, of course, there's a problem here, because Descartes's idea of God may not be all that similar to a complex computer design.
Consider the same case of my child's drawing, but this time I find a picture of a black square box and a label "Very big computer" underneath it. In that scenario, I would be far less likely to have a clear and distinct perception that some mind greater than the child's produced the image. Descartes might deny that his conception of God is indeed like this simple diagram; however, this second scenario is a better analogy to Descartes's notion of God than the first, and, for all the initial plausibility, Descartes's first argument for the existence of God does not appear all that sound.