a property of compound propositions that are true by virtue of both their formal logic and the meaning, or interpretation, of the logical operations contained in them.
While facts, or classes of factual situations, constitute the substance of such propositions—inasmuch as they are the subject of the latter’s constituent elementary propositions—the compound propositions themselves only appear to be descriptions of facts. In essence, they express logically significant connections between statements. The ideas that result from these connections are always true ones, regardless of the area of knowledge or subject matter. The scientific value of self-identical truth lies in its invariability with respect to the contents of ideas and its applicability to the concrete forms in which ideas are expressed. Self-identical truths are part of the established laws of logic; they pertain to and are consistent with any given area of human knowledge—forming the logical fabric, as it were, or logical basis, for the methods of reasoning applied in that area of knowledge.
M. M. NOVOSELOV