Human happiness depends upon theoretical knowledge and practical conduct, as the Philosopher explains in the book On the Soul. But it is not possible by the human intellect alone to arrive at a proper knowledge of the true and the good, because human reason is not capable of comprehending things as they are in reality, as will be explained later. There must therefore be something higher than the human intellect by means of which the good can be defined and the true comprehended in a manner leaving no doubt at all. This can be done only by means of divine guidance. It is incumbent therefore upon every person, out of all laws to know that one divine law which gives this guidance. This is impossible unless we know the basic principles without which a divine law cannot exist. Accordingly the purpose of this work is to explain what are the essential principles of a divine law, and for this reason it is called The Book of Principles. The present work consists of an Introduction and four books.

Excerpted from Sefaria, ספר העיקרים, החברה האמריקאית לפרסומים יהודיים, 1929