What Difference Does It Make?

An argument that never ends

Two friends at a barbecue start arguing over whether a hot dog is a sandwich. One says that bread around a filling makes a sandwich, and a bun is bread. The other says a sandwich needs two separate slices, and a hot dog bun is one piece hinged along the side. Twenty minutes later neither has moved. Then someone asks the obvious question: if you decide it is a sandwich, what happens then? You eat it the same way. It tastes the same. Nobody’s lunch changes.

That question, what happens then, deserves to be taken seriously. Some arguments feel important while they last and turn out to have nothing underneath them. Others sound trivial and turn out to matter a great deal. It would help to have a way of telling the two apart before losing the afternoon.

Who Peirce was

Charles Sanders Peirce (pronounced ‘purse’) was an American logician and scientist who lived from 1839 to 1914. For about three decades he worked for the United States Coast Survey, where his work included precise measurements of gravity. He taught logic at Johns Hopkins University for five years before losing the post, never held a permanent academic job afterward, and died poor. He wrote a great deal, much of it unpublished in his lifetime, on logic and the methods of science.

He is worth hearing because American pragmatism starts with him. In the early 1870s he met regularly with William James and others in Cambridge, Massachusetts, in a discussion group Peirce later recalled as the Metaphysical Club. Out of those conversations came an essay Peirce published in Popular Science Monthly in 1878, “How to Make Our Ideas Clear.” Twenty years later James publicly credited Peirce with the principle of pragmatism, and the movement grew from there.

The pragmatic maxim

Peirce’s question in that essay is what it means to have a clear idea. Being familiar with a word, or even being able to define it, falls short of knowing what you commit yourself to when you use it. His answer became known as the pragmatic maxim, a rule for making the meaning of an idea clear. In his words:

“Consider what effects, which might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.” (Peirce, “How to Make Our Ideas Clear,” 1878, section II)

The sentence is hard going, so here is a paraphrase: to know what you mean by something, work out what difference it would make if it were true; that difference is all you mean. Peirce puts it more briefly in the same section: “Our idea of anything is our idea of its sensible effects.” ‘Sensible’ here means ‘detectable by the senses’, not ‘reasonable’.

Take an ordinary claim: ‘this milk has gone off.’ What do you expect if it is true? It will smell sour. It will form lumps when poured into hot coffee. If you drink much of it, your stomach may object. Now try to imagine milk that has gone off but smells and tastes exactly like fresh milk and does you no harm, now or ever. The claim has come loose from anything you could check or act on, and the maxim says it no longer means anything. The meaning of ‘gone off’ is that bundle of expectations.

Settling empty disputes

Apply the same test to the barbecue. What would follow if a hot dog is a sandwich? Nothing about the food changes. Its taste and price stay fixed whichever word we pick. Once that is seen, the argument turns out to be about vocabulary, and the two friends can simply note that they use a word differently. Peirce draws the general lesson in the same essay: “there is no distinction of meaning so fine as to consist in anything but a possible difference of practice.” Where no practice differs, there is no distinction to fight over.

The maxim works in the other direction too. Suppose a café operates under a regulation that taxes sandwiches at a different rate from other prepared food. Now ‘is it a sandwich?’ has consequences: a different bill, a different line on a form. The question that was empty at the barbecue has real content at the café, because something hangs on the answer. The maxim leaves open who is right. What it supplies is a list of things you would have to look at to find out, and sometimes the discovery that there is nothing to look at.

A harder case. Suppose I replace my old bicycle part by part over ten years until no original piece remains. Is it the same bicycle? Put that way, the question can run forever. Ask what turns on it and it breaks into smaller questions that have answers. Does the frame number match my theft registration? Do I feel the same attachment to it? Once those are answered, I am not sure anything is left over. Some philosophers think something is, and that questions of identity are not exhausted by their practical upshot. I will not try to settle that here.

A word on limits. Peirce’s word ‘conceivably’ widens the test to what would happen under any conditions you can describe, including ones nobody has tried. It is a test of meaning, and it says nothing about whether an idea is profitable or comforting. Scholars disagree about how far that ‘would’ reaches, and about whether the 1878 essay reflects Peirce’s settled view. Later in life he restated the maxim and renamed his position ‘pragmaticism’, partly to separate it from ways others had used his idea. Peirce is a difficult thinker, and I have kept to the simplest version.

Tomorrow, William James takes Peirce’s question and asks what an idea is worth in the living of a life, a move he described with a phrase that has been quoted, and argued over, ever since: ‘cash value’.