Nature does not count nor do integers occur in nature. Man made them all, integers and all the rest, Kronecker to the contrary notwithstanding.

It seems to me that there is a good deal of ballyhoo about scientific method. I venture to think that the people who talk most about it are the people who do least about it. Scientific method is what working scientists do, not what other people or even they themselves may say about it. No working scientist, when he plans an experiment in the laboratory, asks himself whether he is being properly scientific, nor is he interested in whatever method he may be using as method.

The operational approach demands that we make our reports and do our thinking in the freshest terms of which we are capable, in which we strip off the sophistications of millenia of culture and report as directly as we can on what happens.

It is the merest truism, evident at once to unsophisticated observation, that mathematics is a human invention.

Science is what scientists do, and there are as many scientific methods as there are individual scientists.

To find the length of an object, we have to perform certain physical operations. The concept of length is therefore fixed when the operations by which length is measured are fixed that is, the concept of length involves as much as and nothing more than the set of operations by which length is determined.

In general, we mean by any concept nothing more than a set of operations; the concept is synonymous with the corresponding set of operations.