One can divide knowledge of the objective world roughly into two broad categories: first knowledge of Things, which consists in understanding them well enough to be able to classify them according to their qualities, i.e. according to their usefulness for various purposes, and, secondly know- ledge of the Laws which control these Things, which consists in understanding them, with their causes and effects, well enough to be able to predict with fair accuracy what is likely to happen in any particular circumstances. Take knowledge of Things: We shall of course be com- pelled to take as our example a Table, since this appears to be the only piece of furniture which philosophers recognize or possess. If then I say, This table is made of wood (a simple statement about a relatively simple object), I have said something which, though correct enough for most purposes, is inevitably more or less inaccurate, more or less vague and more or less simplified. In the first place, the word table is a general word used to describe a number of different objects which resemble each other in certain useful respects sufficiently for us to have found it convenient in practice to put them in a class and give them a common name. The word wood similarly is a label for a class of substance. Thus neither table nor wood is a definite description of the particular object or substance in question. In the second place, to say that a table is made of wood is seldom strictly accurate and never strictly comprehensive ; it is a simplification, again for convenience, of the real facts which are (say) that it is made of nails, screws, varnish and polish as well as wood. Further- more, these words varnish , nail , etc., are themselves vague generalizations, Varnish, for instance, what is l6 MOTIVES FOR IRRATIONALITY that? If we were trying to be accurate (rather than trying to make life easy) we would have to explain that it consisted of such-and-such chemicals in such-and-such proportions, approximately. A scientist might be able to tell us these proportions with fair accuracy, for it is his job to diminish the inaccuracy of most of our knowledge. But even he would never be able to tell us with absolute exactness what they are, for the concept of exactness is an ideal a comforting mental fantasy; in the objective world there is, as far as we know, no exactness (i.e. no two things have been proved to be devoid of any difference between them) and in our observations of objective phenomena we can do no more than approach exact- ness. Although this may seem a paradox, all exact science is dominated by the idea of approximation. . . . Every careful measurement in science is always given with the probable error, which is a technical term, conveying a precise meaning. 1 The situation is analogous, as will be seen, in the case of all our knowledge of objective phenomena. Every statement we make about things is analysable down to an attempt to place these things, in virtue of one or other of their qualities, in a category appropriate to the particular purpose we have in view at the time. Our simple classifications of phenomena into tables, cheeses, etc., are thus similar in object and method to those of scientists who, with the object of increasing our power to deal with the world, have arbitrarily divided up a large part of its phenomena into categories and have called these categories metals , arthropods , mammals ; , nerves, and so on. Even in these scientific categories there is no absolute exactness ; the mammals all differ in various respects ; there are even animals which fit so badly into any one category that there is argument as to where they belong. More important, it depends on the particular purpose in view into which category a particular phenomenon is placed, e.g. some chemicals may be poison for one purpose and tonics for another, while killing may be murder for some purposes and war for others. However, although these categories are not exact in con- ception although they do not give us an accurate picture of the objective world they are sufficiently differentiated to be of immense help in systematizing our knowledge. The naming 1 Bertrand Russell, The Scientific Outlook, THE DESIRE TO UNDERSTAND IJ of things and the placing of them in categories is thus a sort of simplification (inaccurate but useful all the same) of the extieme complexity of real life. We can never under- stand this full complexity ; as a rule we do not even need to. But we need to understand it to an extent which will help us to deal with it to survive. We therefore simplify it. Knowledge of Things is, however, according to our present classification, only a part of our knowledge of the world. We have also to understand the laws which control these things. (There is, strictly speaking, no sharp division between know- ledge of Things and knowledge of Laws, but I make the division in the same way as all such divisions are made for the sake of convenience.) In other words, we have to know such facts as that water boils when we heat it enough, and that apples, and other things, fall to the ground when their support is withdrawn. These pieces of knowledge, when stated in a more precise form, are applications of laws (in the scientific sense) in that they predict what will happen in certain circum- stances. And in fact all such knowledge is of the same type, though the laws which it invokes vary greatly in the wideness of their application. The application of the law about boiling water is relatively restricted, while that of the law of gravita- tion is relatively very general. Such laws, however narrow in their application, are strictly speaking matters of probability, not of absolute certainty ; for, in the objective world, the concept of absolute certainty is, like that of absolute exactness, an ideal only a comforting fantasy. Though we can be absolutely certain of our own sensations, as I can be certain that I feel hot, we can never be absolutely certain in the sense of there being no possible doubt about anything outside our own minds and sensations. I might, for instance, feel hot, but I cannot be logically certain that there is, in the objective world, an object emitting heat-rays which has caused my sensation. I may have a temperature, or I may have had some whisky ; it is even possible that I am suffering from delusions and that the fire I think I see is not really there at all, I am belabouring this point in order to emphasize the dis- tinction between two common usages of the word certain , In ordinary life it usually means certain for all practical purposes, i.e. so highly probable that it is worth taking AS certain. But it can also mean logically certain 1 or l8 MOTIVES FOR IRRATIONALITY absolutely certain , i.e. capable of indubitable proof in the same way that two plus two can be proved to equal four. 1 This lack of absolute certainty makes it impossible in any case to prove logically that a law is sound. However, this can hardly be said to matter, for the laws value lies, not in its logicality, but in the fact that it enables us to predict what will happen. And if the predictions we base upon it are sufficiently often correct we can in practice ignore the element of uncertainty. A law is in fact a possible hypothesis or generalization which will explain certain observed facts. It is never certain that some other hypothesis might not explain these facts just as well. But if the chosen hypothesis is correct, other facts should be deducible from it. If these new facts are then found by observation to exist, their existence confirms the probability that the hypothesis is valid ; and every such confirmation increases this probability until, as in the case of (say) the laws of motion, the probability becomes so extremely high that the hypothesis is made the basis of scientific research and prediction. The laws of statics, for instance, enable us to build a bridge and to predict with practical certainty that it will not fall down. Similarly our semi-automatic under- standing of natural laws enables us to predict with practical certainty that it is safe to cross the road when we have looked to see that there is nothing coming. Note however that, in addition to the theoretical element of doubt in the laws themselves, there is a further element of doubt in the predictions based on them. Such a prediction says, in effect: It is highly probable that, given certain specific conditions embodying certain causative elements, such- and-such will happen/ And the correctness of the prediction depends on the conditions being in fact what they should be in theory. But this again is never certain, for, as we have seen, even scientific measurement can never be exact, and there may always be some obscure but important causative element (usually while still unnamed and unclassified called the 1 Such splitting of hairs has only incidental relevance here. But, as will be seen later on, the failure to notice the distinction often leads to the tempting but erroneous belief that it must somehow be possible to attain logical certainty in our knowledge of the objective world, i.e. in our reality- thinking. The search for this mares nest of logical certainty is of course a favourite occupa- tion of philosophers. The fact that propositions like 2 plus 2 equals 4 and All A is A can be logically certain is, as will also be seen, no evidence in favour of the mares nests objective existence, since these propositions do not give us any knowledge about the objective world, but merely express our communitys agreement to use certain words in a certain way.
Posted on: Wed, 12 Mar 2014 18:30:39 +0000
Trending Topics
Recently Viewed Topics
© 2015