In his first meditation, Descartes presents his evil demon argument in his reasoning for skepticism. A primary conception to retain in mind as one discusses Descartes’s evil demon argument is that Descartes is not a global skeptic.The argument on the basis of the demon rules out much knowledge that people have regarded the external world, except the knowledge of self, our mind, god, etc. Anything that is perceived via our senses in the external world could be ruled out, too. However, this form of a demon argument is different from the argument that was made as for the sensory illusion errors and dreaming. To understand the difference, consider sensory illusions.
However, in the case of the demon logic, what Descartes introduces is another factor that challenges even the way we perceive. We touch something and it is cold, then we assume it is cold; here there are no illusions. However, Descartes idea of the Demon makes us understand that what we have so far understood to be cold, might not actually be so because of the introduction of another piece of information that is true.
According to epistemic closure, an agent will satisfy closure when some conditions are satisfied. The challenge in first meditation is that the nature and structure of Cartesian skeptical arguments and the responses to the Cartesian skeptical argument would hence have to be understood in order to assume the argument to hold, and the argument cannot be expected to hold valid for all circumstances. The argument is just a possibility that could also exist.