The fact is, that good practice can, in no case, have any solid foundation but in sound theory. This proposition is not more important, than it is certain. For, What is theory? The /whole /of the knowledge, which we possess upon any subject, put into that order and form in which it is most easy to draw from it good practical rules. Let any one examine this definition, article by article, and show us that it fails in a single particular. To recommend the separation of practice from theory is, therefore, simply, to recommend bad practice.

James Mill, Education, in Macvey Napier (ed.) Supplement to the Encyclopædia Britannica, London, 1825