Normal conditions

Normal conditions are a restriction on philosophical arguments, especially in epistemology, in order to avoid objections perceived as digressive. As a reply to objections to an explanation of a phenomenon, e.g. a hypothesis or a theory, it is said, argument X holds under normal conditions. In some cases, the concept of normal conditions tends to be rather blurred and the reply under normal conditions can tend to extend to everything that contradicts an argument. In cases, when the argument of normal conditions comes too often, according to the principle of Occam's Razor another explanation X' has to be found.
In natural science normal conditions term is often used as a less strict substitute for standard conditions. The latter term supposes strict definition of environment parameters, and mentioning the standard, under which "standard conditions" are defined. In technical American English it is often abbreviated as "NC".