The Cancer Journal - Volume 5, Number 1 (January-February 1992)


How does one gain knowledge of the outer world? Our senses perceive it as signals that are put into the organism and processed. Signals are then assembled into patterns that are interpreted with propositions about their nature. Propositions may be sorted into empirical (or a posteriori), and a priori. Empirical propositions are gained by experience, and a priori propositions determine how information is processed (1, 2). A child playing with marbles may learn that when adding two marbles to two other marbles it gets four marbles, which is an empirical statement. But when realizing that "two and two are four" independently of the marbles it played with, the proposition is a priori. In this sense propositions of pure mathematics are a priori. Propositions may be also grouped according to their grammatical content, and whether they provide new information about the world. An analytic proposition is one in which the predicate is part of the subject, e.g., " a tall man is a man', and a synthetic proposition is one that is not analytic, and is generally gained by experience, e.g. "Napoleon was a man".

As long as phenomena do not interact, it appears as if analytic and a priori propositions on one hand, and synthetic and empirical, on the other, are synonymous. The difference between them becomes apparent when propositions are applied to interacting phenomena, particularly if it appears as if one causes the other and we are led to formulate the law of causality. We may then wonder whether this law is analytic or synthetic? In other words, is it part of the outer world, or was it imposed by our mind on the processed signals. Hume proved that the law of causality is not analytic, and yet in spite of being synthetic we can never be certain of its truth. Kant accepted the view that the law of causality is synthetic, but nevertheless maintained that it is a priori (1, 2). In other words, the law of causality describes nature, and yet was not conceived by us empirically. Kant called such propositions "synthetic a priori".

Kant created the "synthetic a priori" concept to account for knowledge of the world that was not gained by empirical means. As Bertrand Russell puts it: "Although none of our knowledge can transcend experience, it is nevertheless in part a priori and not inferred inductively from experience" (1). The concepts belongs to metaphysics that asserts its existence and is less concerned with how "synthetic a priori" knowledge is gained. How does one gain knowledge of the world without experience? The answer is given by the theory of evolution. But first we ought to distinguish between knowledge of the individual and knowledge of the species. The first is gained by experience, while the other is acquired by natural selection.

Even the smallest microbe on earth is guided by "synthetic a priori" knowledge that was conveyed to it by the species. An ameba knows how to avoid some noxious agents even before engulfing them, since carrying in its genome "synthetic a priori" information that is necessary for its survival. Nature selects individuals with most adequate "synthetic a priori" knowledge, and the "less fit" are eliminated. The "synthetic a priori" actually guides animal behavior, and its nature may be understood by studying behavior as done by ethology (3). Each species has a typical behavioral repertoire, known as ethogram that is innate and may be manifested at birth or later. For instance, the newly hatched chick knows that its mother is waiting outside the egg shell. Its expectations are nurtured by a priori knowledge that was not gained by experience. The act of mother selection, coined by K. Lorenz as imprinting, has to be distinguished from learning from experience. E.H. Hess demonstrated what happens when the chick's expectations are not fulfilled. He substituted for the real mother a model with a loudspeaker inside, that moved by mechanical means. The imprinted duckling followed the model as if it were his real mother (4). Outside the laboratory it would have paid for this mistake with its life and "selected out" from the species.

Immunology presumes that the organism carries "synthetic a priori" knowledge of antigens, and when necessary produces antibodies against them. Not only antigens, but any noxa that was encountered by the species since life began, had to leave its imprints on our genome. These are embodied as strategies that are triggered when noxae hit the organism (5). The major task of medicine is to mobilize a priori" knowledge for the patient's own benefit. In this forum we are concerned mainly with one disease that still evades our understanding and ask: What is the "synthetic a priori" knowledge of cancer that could be harnessed in order to heal it?

G. Zajicek


1. Russell B. A History of Western Philosophy. Simon and Schuster, New York, 1945.
2. Steiniz Y. In Defence of Metaphysics. Dvir Publishing House, Tel Aviv, 1990.
3. Eibl-Eibesfeldt I. Ethology, the Biology of Behavior. Holt Reinhart and Winston Inc., 1975.
4. ibid p. 260.
5. Zajicek G. What is a disease? Cancer J 4, 296, 1991.