As inquiring agents modify their evolving doctrines, they come to believe where they were initially doubtful. Conjectures or hypotheses are thereby converted into settled assumptions free from serious doubt and, therefore, counted as certainly true. Such erstwhile conjectures are shifted to the status of evidence or knowledge and are deployed as premises in subsequent inquiries (pending future reconsideration).

Inquiries that terminate with the settling of an issue are provoked by the presence of doubt. To be sure, the presence of doubt does not automatically induce the doubter to engage in inquiry. We attach greater urgency to the solution of some problems than to the solution of others, and often disagree, and disagree intensely, as to the priority to be attached to various unsettled issues. Even so, when agents seek to justify the termination of inquiry by adding to the body of settled assumptions some proposed solution to the problem under investigation, their effort at justification is predicated on a distinction between those propositions taken for granted as settled and beyond reasonable doubt, and others that are not regarded as certainly true but as conjectural, more or less probable or improbable and, hence, as both possibly true and possibly false. And, given that distinction, the effort to justify the conversion of a conjecture into a certainty is an effort to justify a change in the set of assumptions accepted as evidence and as certainly true and, with this alteration, to institute a change in the way in which truth value-bearing claims are separated into those whose truth is seriously possible and those whose truth is not seriously possible.