The development of logic, at least of formal logic, in the nineteenth century was largely independent of the general development of philosophy during the same period. Of the logicians considered in the preceding section only C. S. Peirce and perhaps William Hamilton were of importance in branches of philosophy other than logic, and the persons who were of most importance in other branches of philosophy contributed nothing whatsoever to technical developments of the sort here described. These persons did not ignore logic altogether, however, nor did competent logicians entirely ignore them. It will be helpful, therefore, to break the chronological order at this point and to glance back at these philosophical developments and influences.

In the nineteenth century, as in the eighteenth, there were divergent Continental and British philosophical influences, but the Continental stream, stemming from Immanuel Kant...