Hossein Jorjani
First publication: 2026 – 10 – 15
Scientific and philosophical arguments depend upon the continuity of concepts and the stability of the questions being investigated. Yet neither continuity can be taken for granted. A word may retain its spelling while changing its meaning, and an argument may retain its general subject while changing the particular phenomenon it seeks to explain. Such changes are not necessarily objectionable. Concepts evolve, and investigations frequently lead to new questions. Difficulties arise when these changes remain unacknowledged and conclusions reached under one meaning or concerning one object are presented as though they applied to another.
Several related phenomena should therefore be distinguished: semantic shift, semantic slippage, equivocation, and explanandum shift.
Semantic shift refers to a change in the meaning of a word or expression, commonly across historical periods, intellectual traditions, or contexts of use. The word dialectic, for example, has designated different intellectual practices and philosophical conceptions, from methods of questioning and argumentation to purported principles governing the development of reality. Such changes are not inherently erroneous. They form part of the historical development of language and concepts. Problems arise when the continuity of a term is taken as evidence of continuity in its meaning or theoretical function.
Semantic slippage refers more specifically to movement between meanings within a discussion or argument. The movement may be gradual, unnoticed, or insufficiently marked. Consider the word idealism. In ordinary language, it may designate the possession of ideals and a commitment to realizing them. In philosophy, it may designate positions concerning the fundamental nature of reality or the relationship between mind and world. A discussion may begin with idealism in the first sense and gradually introduce claims belonging to the second. If the change is recognized, the discussion may legitimately address both meanings. If it is not, the apparent continuity of terminology can conceal a discontinuity of concepts.
Equivocation is a more specific argumentative error. It occurs when an inference depends upon treating different meanings of the same word or expression as though they were identical. If someone argues that idealists pursue ideals and then concludes that idealists therefore deny the mind-independent existence of material reality, the conclusion does not follow. The argument moves between two meanings of idealism without establishing a relationship that would justify the inference. Equivocation is thus not merely the presence of ambiguity, but the use of that ambiguity in a purported inference.
A different problem arises when the meaning of the principal terms remains relatively stable, but the explanandum changes. The explanandum is what an explanation seeks to explain: a specified phenomenon, event, process, relationship, or state of affairs. It must be distinguished from the explanans, the propositions, conditions, mechanisms, or causes offered to explain it.
Suppose an inquiry begins by asking how surplus value is produced under capitalist relations of production. It then introduces factors such as international demand, technological change, and government policy to explain variations in the amount of surplus value. Finally, it turns to the historical transformation of capitalism. All three inquiries concern capitalism, and all may be legitimate. Nevertheless, they do not have the same explanandum. The production of surplus value, variation in its magnitude, and the transformation of capitalist society are different objects of explanation. An explanation of one cannot automatically be treated as an explanation of the others.
An explanandum shift occurs when an inquiry moves from one object of explanation to another. The shift itself need not be erroneous. Indeed, scientific progress often depends upon recognizing that an initially formulated question must be modified or replaced. The methodological problem arises when the shift remains unacknowledged and an explanation developed for the second object is presented as though it answered the original question.
This problem is particularly important in the investigation of complex systems. The boundaries of the object being explained may be expanded or contracted during an argument. An explanation initially concerned with a national economy may gradually incorporate the world economy until the latter becomes the effective object of investigation. The expanded inquiry may be valuable, but it cannot establish a conclusion about the original object merely by redefining its boundaries. The same caution applies when an argument moves from explaining a particular process to explaining the system within which that process occurs.
Equivocation and unacknowledged explanandum shifts therefore share a methodological feature, although they operate at different levels. In equivocation, the same expression is retained while its meaning changes. In an explanandum shift, the same general subject may be retained while the question requiring explanation changes. In both cases, apparent continuity can conceal a discontinuity on which the argument depends.
A related logical error is traditionally called ignoratio elenchi, often rendered as an irrelevant conclusion or missing the point. An argument may successfully establish a proposition that is different from the proposition it was intended to establish. An unacknowledged explanandum shift can contribute to this error, but the two are not identical. Changing the explanandum concerns the organization of an inquiry; reaching an irrelevant conclusion concerns the relationship between an argument’s conclusion and the proposition at issue. An explanandum shift becomes especially problematic when the answer to the substituted question is offered as an answer to the original one.
These distinctions also clarify the difference between conceptual development and argumentative inconsistency. A concept may legitimately acquire a new meaning. An investigation may legitimately redefine its object. An argument may even examine several meanings or several explananda simultaneously. What matters is whether the distinctions are maintained and whether the transitions are made explicit and justified. Methodological consistency does not require that concepts or questions remain permanently unchanged. It requires that changes not be concealed by the continuity of words, subject matter, or argumentative presentation.
The general principle may be stated as follows: continuity of terminology does not guarantee continuity of meaning, and continuity of subject matter does not guarantee continuity of the object of explanation.
This principle has consequences for both scientific and philosophical inquiry. Before accepting an argument, one should establish whether its principal concepts retain the meanings assigned to them and whether its conclusions address the explanandum originally specified. If either has changed, the change must be identified and its consequences examined. Otherwise, an argument may appear to have demonstrated a proposition that it has never actually established.
The purpose of these distinctions is not to prevent conceptual change or the reformulation of questions. Both are indispensable to the development of knowledge. Their purpose is to distinguish legitimate intellectual movement from unnoticed substitution. An argument may change direction, but it should not claim to have arrived at its original destination when it has answered a different question.
