[William] James argued at length for a certain conception of what it means for an idea to be true. This conception was, in brief, that an idea is true if it works. (Stapp 2009, 60)

James’s proposal was at first scorned and ridiculed by most philosophers, as might be expected. For most people can plainly see a big difference between whether an idea is true and whether it works. Yet James stoutly defended his idea, claiming that he was misunderstood by his critics.

It is worthwhile to try and see things from James’s point of view.

James accepts, as a matter of course, that the truth of an idea means its agreement with reality. The questions are: What is the “reality” with which a true idea agrees? And what is the relationship “agreement with reality” by virtue of which that idea becomes true?

All human ideas lie, by definition, in the realm of experience. Reality, on the other hand, is usually considered to have parts lying outside this realm. The question thus arises: How can an idea lying inside the realm of experience agree with something that lies outside? How does one conceive of a relationship between an idea, on the one hand, and something of such a fundamentally different sort? What is the structural form of that connection between an idea and a transexperiential reality that goes by the name of “agreement”? How can such a relationship be comprehended by thoughts forever confined to the realm of experience?

So if we want to know what it means for an idea to agree with a reality we must first accept that this reality lies in the realm of experience.

This viewpoint is not in accord with the usual idea of truth. Certain of our ideas are ideas about what lies outside the realm of experience. For example, I may have the idea that the world is made up of tiny objects called particles. According to the usual notion of truth this idea is true or false according to whether or not the world really is made up of such particles. The truth of the idea depends on whether it agrees with something that lies outside the realm of experience. (Stapp 2009, 61)

Now the notion of “agreement” seems to suggest some sort of similarity or congruence of the things that agree. But things that are similar or congruent are generally things of the same kind. Two triangles can be similar or congruent because they are of the same kind. Two triangles can be similar or congruent because they are the same kind of thing: the relationships that inhere in one can be mapped in a direct and simple way into the relationships that inhere in the other.

But ideas and external realities are presumably very different kinds of things. Our ideas are intimately associated with certain complex, macroscopic, biological entities—our brains—and the structural forms that can inhere in our ideas would naturally be expected to depend on the structural forms of our brains. External realities, on the other hand, could be structurally very different from human ideas. Hence there is no a priori reason to expect that the relationships that constitute or characterize the essence of external reality can be mapped in any simple or direct fashion into the world of human ideas. Yet if no such mapping exists then the whole idea of “agreement” between ideas and external realities becomes obscure.

The only evidence we have on the question of whether human ideas can be brought into exact correspondence with the essences of the external realites is the success of our ideas in bringing order to our physical experience. Yet success of ideas in this sphere does not ensure the exact correspondence of our ideas to external reality.

On the other hand, the question of whether ideas “agree” with external essences is of no practical importance. What is important is precisely the success of the ideas—if the ideas are successful in bringing order to our experience, then they are useful even if they do not “agree”, in some absolute sense, with the external essences. Moreover, if they are successful in bringing order into our experience, then they do “agree” at least with the aspects of our experience that they successfully order. Furthermore, it is only this agreement with aspects of our experience that can ever really be comprehended by man. That which is not an idea is intrinsically incomprehensible, and so are its relationships to other things. This leads to the pragmatic [critical realist?] viewpoint that ideas must be judged by their success and utility in the world of ideas and experience, rather than on the basis of some intrinsically incomprehensible “agreement” with nonideas.

The significance of this viewpoint for science is its negation of the idea that the aim of science is to construct a mental or mathematical image of the world itself. According to the pragmatic view, the proper goal of science is to augment and order our experience. A scientific theory should be judged on how well it serves to extend the range of our experience and reduce it to order. It need not provide a mental or mathematical image of the world itself, for the structural form of the world itself may be such that it cannot be placed in simple correspondence with the types of structures that our mental processes can form. (Stapp 2009, 62)

James was accused of subjectivism—of denying the existence of objective reality. In defending himself against this charge, which he termed slanderous, he introduced an interesting ontology consisting of three things: (1) private concepts, (2) sense objects, (3) hypersensible realities. The private concepts are subjective experiences. The sense objects are public sense realities, i.e., sense realities that are independent of the individual. The hypersensible realities are realities that exist independently of all human thinkers.

Of hypersensible realities James can talk only obliquely, since he recognizes both that our knowledge of such things is forever uncertain and that we can moreover never even think of such things without replacing them by mental substitutes that lack the defining characteristics of that which they replace, namely the property of existing independetly of all human thinkers.

James’s sense objects are courious things. They are sense realities and hence belong to the realm of experience. Yet they are public: they are indepedent of the individual. They are, in short, objective experiences. The usual idea about experiences is that they are personal or subjective, not public or objective.

This idea of experienced sense objects as public or objective realities runs through James’s writings. The experience “tiger” can appear in the mental histories of many different individuals. “That desk” is something that I can grasp and shake, and you also can grasp and shake. About this desk James says:

But you and I are commutable here; we can exchange places; and as you go bail for my desk, so I can bail yours. This notion of a reality independent of either of us, taken from ordinary experiences, lies at the base of the pragmatic definition of truth.

These words should, I think, be linked with Bohr’s words about classical concepts as the basis of communication between scientists. In both cases the focus is on the concretely experienced sense realities—such as the shaking of the desk—as the foundation of social reality. From this point of view the objective world is not built basically out of such airy abstractions as electrons and protons and “space”. It is founded on the concrete sense realities of social experience, such as a block of concrete held in the hand, a sword forged by a blacksmith, a Geiger counter prepared according to specifications by laboratory technicians and placed in a specified position by experimental physicists. (Stapp 2009, 62-63)