When skeptical, curious, free-thinking persons discuss religious topics, inevitably the question of 'labeling' will present itself. At some point, a skeptical person will be asked something like: 'so, are you atheist or agnostic'? Understanding the definitional issues presented by these terms is very important for skeptics -- and for all interested persons, for that matter -- because oftentimes these issues can lead to confusion and consequent vulnerability in the context of debate. The most common definition of an 'atheist' is a person who denies the 'possibility' of the existence of god; in other words, the person believes that there is no chance at all that such a being could exist. This is subtly but significantly different than simply expressing personal disbelief in a supreme being, because to deny even the possibility of existence implies a kind of certainty which most people would probably be reluctant to profess. The popular definition of an agnostic, by contrast, is one who strongly doubts the existence of a supreme being, but does not deny the possibility that such a being could exist. In certain limited contexts these definitions are not necessarily problematic since they represent two positions which are meaningfully different; however, in a general sense, they may be problematic because a curious but unsophisticated person could become overwhelmed by them and wrongly classify themselves as a consequence. In fact, to most people it would probably seem unreasonable for anyone to classify themselves as 'atheist' with the definition given above because denying the possibility of a being appears to require 'infinite' or near infinite knowledge. In most contexts, the best definitions of these terms can be stated as follows: an 'atheist' is one who personally disbelieves in the existence of god due to non-involvement with religion in general, and an 'agnostic' is one who is interested in religion but doubts the existence of god due to skepticism. In most cases these definitions will work better than the previous two because the differences between them are clearer and they reflect a more 'common sense' approach to the issue. The structure of the word 'atheism', for example, indicates that one is a 'non-theist' or 'non-believer of theism'; there is nothing in the word itself which would imply a definition as sweeping as the one which is most commonly used. In short, if you want to determine whether you are an atheist or an agnostic, just ask yourself: 'do I disbelieve in the existence of god because of a general lack of support for religion, or because I have retained a skepticism even after being involved with religion for a long period of time?' For most purposes, this works best, because hardly anyone is prepared to make a claim as bold as: 'I do not just disbelieve in god, I absolutely deny even the chance that such a being could exist at any point in the future!' Labeling is not usually a very 'pleasant' thing to do; these are best 'popular' definitions for approaching the question of 'atheist or agnostic' as they are more likely to spark healthy, intelligent discussion.