A justificatory belief system is a complex of interdependent themes and arguments. The whole, typically, has an intricate life: evolving, subject to piecemeal addition or subtraction, to internal shifts rearranging its constituent elements, to critical stricture, defensive reinforcement, creative modification, and so on. It is not always easy in the circumstances to estimate the exact importance of a given element of the whole, to know how much depends on its particular strength. Yet some elements are obviously more central strategically than others, and if it can be shown of any such central element that it is in fact intellectually flimsy, then, other things equal, this weakens the chain of justification in which it is a link.