 This account of necessary and sufficient conditions is particularly apposite in dealing with logical inferences. For example, from the truth of a conjunction, it can be inferred that each component is true (if “p and q” is true, then “p” is true and “q” is true). Suppose, then, that it is true that it is both raining and sunny. This is a sufficient condition for “it is raining” to be true. That it is raining is—contrariwise—a necessary condition for it being true that it is both raining and sunny. A similar account seems to work for conceptual and definitional contexts. So if the concept of memory is analysed as the concept of a faculty for tracking actual past events, the fact that an event is now in the past is a necessary condition of my presently recollecting it. If water is chemically defined as a liquid constituted mainly of H2O, then if a glass contains water, it contains mainly H2O. That the glass contains mostly H2O is a necessary condition of its containing water.