The fact of human liberty and will limits, but does not exclude, the use of deductive and quantitative methods in the social sciences. When large numbers of individuals are examined, we find many examples of the regularity with which certain events repeat themselves. Again, the cardinal nature of economic phenomena, such as utility, cannot exclude entirely every use of mathematics. It shoud be recalled that, in every branch of science , the use of mathematics can lead to incorrect solutions if the basic hypotheses are at fault. Nevertheless, it should be borne in mind that it is not necessary for an hypothesis, and therefore for the result supplied by the application of mathematical tools to that hypothesis, to correspond in every detail to reality. Other examples of unfounded criticisms of mathematics in economics may be mentioned ; the necessity for continuous functions ; the use of extrapolations ; the neglect of time factors and of irreversibility. None of these criticisms resist examination. It would no doubt be desirable to see more economists become competent mathematicians. But even without this it should be possible for economists to examine objectively the results secured by mathematicians. Extremely important in this respect is the need to test mathematical models just as all models in physics are tested. In general, it may be said that, whatever may be the present defects of econometrics, it has produced results, notably in forecasting, which it would have been impossible to attain without the use of mathematics.