Arbitrary/Possible/Probable/Certain Scale
also Peikoff's validation ladder · Validation Ladder
Peikoff's Objectivist scheme rating an idea arbitrary, possible, probable, or certain, with ideas climbing toward certainty as evidence accumulates.
In Objectivism: The Philosophy of Ayn Rand, Leonard Peikoff grades an idea as arbitrary, possible, probable, or certain. An idea is said to gain validation and rise to the next status as supporting evidence accumulates. The “arbitrary” rung is reserved for claims advanced with no evidence at all (see the arbitrary), which Objectivism dismisses rather than rates as false.
CF’s verdict is two-sided. On one hand, it credits the scheme: by collapsing the apparent continuum of credibility into just four discrete categories, the ladder is far better than the usual practice of assigning percentages (101 values from 0 to 100), because a small number of categories aids error correction — a thing 1% short of a typical “probable” case is just probable, the gap being mere variation within a category. This is the same digital advantage CF builds its own epistemology on.
On the other hand, CF rejects the ladder’s core. It is a degrees-of-certainty scheme: it ranks ideas by how good they are along a path toward certainty, and Objectivism even treats the four steps as points on an analog continuum. CF’s objection to amounts-of-goodness is not about numbers; it applies to any such ranking, numeric or not. CF instead uses binary evaluation — an idea is refuted or non-refuted for a given goal — and holds even confident conclusions tentatively. So the ladder’s verdicts get replaced by yes-or-no judgments, not finer gradations.