F. because he drank and was dirty.

The difference between a medical cause in the generalised sense, (where cause means a defining correlative for a concept), and a medical cause in the particular sense (when we seek to find out or state the antecedent without which this man would not be as he is here and now) is one of enormous importance, and one that should be constantly borne in mind when discussion is commenced. It is true that it involves the oldest of logical and metaphysical problems in respect of scientific thought—the question of universals and particulars; but that does not make it any the more easily shirked. Its relevance to the question of cancer is this: that the proof of the production of cancer in men or in animals under one set of circumstances does not warrant us in saying that that set of circumstances as known to us involves all the factors without which cancer cannot occur. And, even if research work demonstrated that, in every case now called cancer, some parasite or growth-form, some irritating factor that can be isolated, does actually obtain, unless it could be shewn that this parasite or factor is never found except where there is cancer as we now define it, we should have to proceed to investigate why and how cancer does not always occur when this factor is present. Just so are we at present seeking to explain why and how, of so many persons exposed to infection by Koch’s bacillus, only certain ones do become diseased. If we find that only those persons who possess a character that we may call “X” become infected, we shall then have to say that, not Koch’s bacillus, but the character “X” is “the” cause of tuberculosis. It is thus that science progresses: not by making the absolute and positive discoveries that the public is taught to expect, but by arranging and rearranging our experiential knowledge, as such grows, in terms of so-called laws and generalisations, that are found progressively convenient. But such laws and generalisations are not necessarily the one more “true” than the other, except in relation to the knowledge that they summarize. If such considerations as these were more frequently borne in mind, there would be less unconscious deception, less disappointment, and greater economy in work and thought.

Explanations of the causation of cancer have been sought in many directions; and three chief theories have been set out. The most important, and the most interesting from the point of view of the practising physician, is that which considers cancer as provoked by long continued irritation under certain circumstances. This doctrine seems more “true” in respect of the Carcinomata—the cancers of the adult and the old, and of tissues in contact with the extra-personal world—than it is in respect of the Sarcomata—the cancers of the young, and of those inner parts not exposed to irritation by contact with the world. Yet sarcomata in real life do often seem to follow injury, and the tissues in which they form may be obnoxious to injurious influences of which we know nothing.

Another view is that cancer may be due to a parasite of some kind or another. Certainly, so far as some lower animals are concerned, this is true, for certain rat and mice cancers are now known definitely to be associated with parasites. But then we may say, and properly, that in such cases the parasites are merely acting as do other irritants, and are not “specific” causes of cancer.

The third doctrine, or set of doctrines, regards cancers as arising when parts of the body (or rather, elements in the tissues of certain parts) no longer act in due subordination to the needs of the whole organism, but comport themselves “anti-socially”: developing irregularly; propagating themselves illegitimately; and so becoming parasitic to the commonwealth of the body. Those who hold this will admit that, in many cases, this revolutionary tendency is one provoked by irritation and the like: that sometimes it is a mere manifestation of irregular decay; and that, when it occurs in young subjects, it is because some islets of tissue have become misplaced, tucked away, ill-formed, and hampered in development, and so liable to provoke trouble later under stress of greater or less urgency. Such a view has much plausibility; there are flaws in a steel girder; there are tucked-in edges in even the best bound book, and there are developmental errors in most of us.

Moreover, there is Dr Creighton’s doctrine of physiological resistance. A part not put to its proper use is more apt than another to become cancerous. Certainly, unmarried women are more liable than are married to suffer cancer of the breast or ovary. Yet married women are more apt than unmarried to suffer cancer of the womb. Are we to say that in these latter there has been physiological misuse, or irritation produced by unhealthy child-bearing? So far is the problem removed from simplicity!

On the other hand, it is certainly as true as ever, that the gods still cancel a sense misused, and, if we leave out of account for the moment the cases in which cancer seems due to developmental error—and who can say whether even then a child does not suffer vicariously for some physiological transgression by its parents?—the doctrine that cancer is due to irritation, whether produced by a clay pipe, hot drinks, constipation, or crude paraffin, does not really tell us much more than that. The difficulty is this: How to walk in the way of physiological righteousness, and how to preach it, without falling into a dogmatism as stupid as unbelief? Mr Wright tells us how, in medieval times, the Church declared cancer of the tongue to be sometimes a judgment on sinners for their blasphemy. Well, I for one, am not prepared to limit the “misuse” that entails physical disease and suffering to misuse in the material, or physiological sense. Organs, through the nerves of the “sympathetic”, are directly connected with the play of emotions and of feeling-states. I am not sure that investigation would not shew a correlation—sometimes—between certain persistent and voluntary mental states (morbid mental states, that is) and the development of cancer in certain organs. The “argument” that cancer is infrequent in lunatic asylums, where the majority are mindless rather than wrongly thoughtful, evades the question.

The quest for a single causal factor, whose “discovery” will lead us to “abolish cancer”, is then, it would seem, just one more hunt for the philosopher’s stone. Yet, to use the formula of “right living” does not seem to be merely a verbal solution of the difficulty.

If we agree that to live rightly is the best insurance we can make against cancer, we are probably stating, as compendiously as possible, all we do and shall ever know, in respect of the causation of cancer. It is then our duty to ascertain how to live rightly in every sense of the word, and we may so come to realise that almost every one of what we call the blessings of civilisation has been purchased at the expense, in some respect, of right living. For this, heavy interest has to be paid, and even the efforts of science to put matters right seem too often not more than the borrowing of fresh capital to pay off old debts. It is right to call attention to the fact that certain “uncivilised” races, who live healthily and naturally in respect of food, drink, and sexual activity, do not suffer from cancer. But it is wrong to suggest that therefore we should adopt either their dietetic or their sexual customs. What is one man’s meat is another man’s poison. Adjustment to our surroundings, right living here and now is what we need. Though Papuans and Sikhs may be very properly adjusted in their contexts, it is not their adjustments that may best suit our cases.

This problem—that of right living—is the problem of prevention of cancer put upon the broadest basis. But, until or unless we work this out, we have to consider how best to avail ourselves of the knowledge already in our possession. Herein is one merit of Mr Wright’s plan. He tells people what, in his judgment, they can best do, here and now. It is a plan to be discussed; but, let it be clearly understood, it is one submitted by the author for individual consideration and action. Supposing it to be found, on analysis and trial, of real value, a cry might at once be raised for its putting into execution by central or local provision of the necessary facilities: at first for voluntary acceptance, then for compulsory adoption. Nothing could be a greater error. In matters of health what is advantageous for the individual is often not so, or even grossly disadvantageous, for the State.