“All rational knowledge is either material, and concerns some objects, or formal, and is occupied only with the form of understanding and reason itself and with the universal rules of thinking, without regard to distinctions among objects. formal philosophy is called logic. Material philosophy, however, which has to do with definite object objects and the laws to which they are subject, is divided into two parts. This is because these laws are either laws of nature or laws of freedom. The science of the former is called physics, and that of the latter ethics. The former is also called theory of nature and the latter theory of morals.”

“Political realism believes that politics, like society in general, is governed by objective laws that have their roots in human nature. In order to improve society it is first necessary to understand the laws by which society lives. The operation of these laws being impervious to our preferences, men will challenge them only at the risk of failure.Realism, believing as it does in the objectivity of the laws of politics, must also believe in the possibility of developing a rational theory that reflects, however imperfectly and one-sidedly, these objective laws. It believes also, then, in the possibility of distinguishing in politics between truth and opinion — between what is true objectively and rationally, supported by evidence and illuminated by reason, and what is only a subjective judgment, divorced from the facts as they are and informed by prejudice and wishful thinking.”

“Every industrious man, in every lawful calling, is a useful man. And one principal reason why men are so often useless is that they neglect their own profession or calling, and divide and shift their attention among a multiplicity of objects and pursuits.”

“As students, we have all known two types of teachers, the pedantic and the inspiring. The former have a definite method and operate according to well-established habits; the latter need neither, because they know the subject through and through, Indeed, we may say that teaching methods, which generate subjective habits, are but poor substitutes for the kind of objective intimacy with the subject matter to be taught, which we call 'habitus”

“The peculiarity of the evidence of mathematical truths is, that all the argument is on one side. There are no objections, and no answers to objections. But on every subject on which difference of opinion is possible, the truth depends on a balance to be struck between two sets of confliting reasons. Even in natural philosophy, there is always some other explanation possible of the same facts; some geocentric theory instead of heliocentric, some phlogiston instead of oxygen; and it has to be shown why that other theory cannot be the true on: and until this is shown, and until we know how it is shown, we do not understand the grounds of our opinion. But when we turn to subjects infinitely more complicated, to morals, religion, politics, social relations, and the business of life, three-fourths of the arguments for every disputed opinion consist in dispelling the appearances which favour some opinion different from it.”

“The present writer had occasion, some time ago, to call attention to the succession of layers of "laws of nature," each layer containing more general and more encompassing laws than the previous one and its discovery constituting a deeper penetration into the structure of the universe than the layers recognized before. However, the point which is most significant in the present context is that all these laws of nature contain, in even their remotest consequences, only a small part of our knowledge of the inanimate world. All the laws of nature are conditional statements which permit a prediction of some future events on the basis of the knowledge of the present, except that some aspects of the present state of the world, in practice the overwhelming majority of the determinants of the present state of the world, are irrelevant from the point of view of the prediction.”