The contrast between realism and idealism, implied in the use of either term, evidently has its source in the distinction we make between subject and object, idea and reality, or sign and thing signified. This is a natural operation of the human mind, for it belongs to the essence of rational behavior that we can distinguish ourselves as knowing subjects from the objects of our knowledge, and can employ ideas or words to refer to or signify realities independent of them. Normally our attention in knowing, speaking, listening, or reading is not focused upon the ideas or words we use, far less upon ourselves, but upon the realities they signify or indicate beyond themselves. Hence in our regular communication with one another we use and interpret signs in the light of their objective reference. Thus the natural operation of the human mind would appear to be realist.
We use these distinctions, then, between subject and object, idea and reality, or sign and thing signified, naturally and unreflectingly, and only turn a critical eye upon them when something arises to obscure signification, such as a break in the semantic relation. Much now depends upon where the emphasis falls, upon the signifying pole or the objective pole of the semantic relation. that is, upon idea or reality, upon sign or thing signified. In this state of affairs the contrast between idealism and realism arises out of an oscillation in emphasis from one pole of the semantic relation to the other. The distinction sharpens into a conflict, however, when the two poles are extended to a breaking point or when the relation between them is disrupted through some dichotomy of thought. However, since the relation between idea and reality or sign and thing signified is never completely severed, there seems to be a regular tendency, as one extreme position is corrected in respect of the other, for each to pass over into the other, to that idealism sometimes passes over into a form of realism and realism passes over into a form of idealism. For example, in the dialectical relation that arises out of a split between theoretical and empirical factors in natural science, an emphasis upon mathematics separated from experience may end up in a mechanical and materialist understanding of the world, while an emphasis upon sense experience as the ultimate ground of knowledge may end up in a rationalist empiricism or even a conventionalism. Virtually the same dialectic arises in theology between radically divergent approaches to the understanding of Christ traditionally characterized as "dark" and "ebionice," for in modern as in ancient Christologities each tends to turn into a form of the other.
It may be noted that when the semantic relation between idea and reality or between sign and thing signified is not completely severed but only damaged, our thought nevertheless becomes trapped in distorting ambiguities which require correction. It is within the context of this problematic state of affairs, and on the ground of some form of epistemological dualism that underlies it, that coherence and correspondence theories of truth have continually been thrown up in the history of thought. Who has always been at stake is a distorting refraction in the ontological substructure of knowledge. The lesson that is constantly being taught is that there can be no satisfactory theory of truth within the brackets of a dualist frame of thought, for it can only yield the oscillating dialectic between coherence and correspondence. There can be no way forward except through a rejection of dualist modes of thought in an integration of empirical and theoretical components in knowledge and of form and being in our understanding of reality. That would restore the integrity of the semantic reference of idea and sign to reality, in which reality would have objective priority over all our conceiving and speaking of it. Strictly speaking, the contrast, let alone the conflict, between realism and idealism would not then arise, nor would the distinction between a coherence and a correspondence view of truth which depends on a disjunction between form and being.
To return to the meaning of realism, we shall use the term, not in an attenuated dialectical sense merely in contrast to idealism, nominalism, or conventionalism, but to describe the orientation in thought that obtains in semantics, science, or theology on the basis of a nondualist or unitary relation between the empirical and theoretical ingredients in the structure of the real world and in our knowledge of it. This is an epistemic orientation of the two-way relation between the subject and object poles of thought and speech, in which ontological primacy and control are naturally accorded to reality over all our conceiving and speaking of it. (T. F. Torrance, Reality and Evangelical Theology: The Realism of Christian Revelation, 58-60)
