Lecture 1 — The definition of “principle”

In one sense the term “principle” means that from which someone first moves something; for example, in the case of a line or a journey, if the motion is from here, this is the principle, but if the motion is in the opposite direction, this is something different.

In another sense, principle means that from which a thing best comes into being, as the starting point of instruction. For sometimes it is not from what is first or from the starting point of the thing that one must begin, but from that from which one learns most readily.

Again, “principle” means that first inherent thing from which something is brought into being, as the keel of a ship and the foundation of a house, and as some suppose the heart to be the principle in animals, and others the brain, and others anything else of the sort.

In another sense it means that non-inherent first thing from which something comes into being; and that from which motion and change naturally first begins, as a child comes from its father and mother, and a fight from abusive language.

In another sense “principle” means that according to whose will movable things are moved and changeable things are changed—in states, for example, princely, magistral, imperial, or tyrannical power are all principles. And so also are the arts, especially the architectonic arts, called “principles.”

And that from which a thing can first be known is also called a “principle” of that thing, as the postulates of demonstrations.

And causes are also spoken of in the same number of senses, for all “causes” are “principles.”

Therefore, it is common to all principles to be the first thing from which a thing either is, comes to be, or is known. And of these some are intrinsic and others extrinsic. And for this reason nature is a principle, and so also is an element, and mind, purpose, substance, and the final cause. For good and evil are the principles of both the knowledge and the motion of many things.

Principle

749. Having established in the preceding book the things that pertain to the consideration of this science, here the Philosopher begins to deal with the things that this science considers. And since the attributes considered in this science are common to all things, they are not predicated of various things univocally, but in a prior and subsequent way, as has been stated in book 4 [535].

Therefore, first [751], he distinguishes the meanings of the terms which come under the consideration of this science.

Second [751], he begins to deal with the things that come under the consideration of this science. He does this in the book 6, which begins with the words, the principles and causes (1025b3).

Now, since it is the office of each science to consider both its subject and the properties and causes of its subject, this fifth book is accordingly divided into three parts.

First, he establishes the various senses of the terms which signify causes;

second (1015b16; [843]), the various senses of the terms which signify the subject or parts of the subject of this science, at the term “one”**;

third (1021b12; [1034]), the various senses of the terms which signify the properties of being as being, at that thing is said to be perfect.

The first part is divided into two members.

First, he distinguishes the various senses in which the term “cause” is used.

Second (1015a20; [827]), he explains the meaning of a term which signifies something associated with a cause—the term “necessary”—for a cause is that on which something else follows of necessity, at necessary means.

The first part is divided into two members.

First, he distinguishes the various senses of the terms which signify cause in a general way.

Second (1014b16; [808]), he gives the meaning of the term which signifies a special kind of cause, namely, the term “nature,” at nature means.

750. The first part is divided into three members.

First, he gives the various meanings of the term “principle”;

second (1013a24; [763]), of the term “cause,” at in one sense the term “cause”;

and third (1014a26; [795]), of the term “element,” at the inherent principle.

He follows this order because the term “principle” is more common than the term “cause,” for something may be a principle and not be a cause—for example, the principle of motion is said to be the point from which motion begins. Again, a cause is found in more things than an element is, for only an intrinsic cause can be called an element.

In regard to the first he does two things.

First, he gives the meanings of the term “principle.”

Second (1013a17; [761]), he reduces all of these to one common notion, at therefore, it is common.

751. Now, it should be noted that, although a principle and a cause are the same in subject, they nevertheless differ in meaning; for the term “principle” implies an order or sequence, whereas the term “cause” implies some influence on the being of the thing caused.

Now an order of priority and posteriority is found in different things, but according to what is first known by us, order is found in local motion, because that kind of motion is more evident to the senses. Further, order is found in three kinds of things, one of which is naturally associated with the other—namely, continuous quantity, motion, and time. For insofar as there is priority and posteriority in continuous quantity, there is priority and posteriority in motion; and insofar as there is priority and posteriority in motion, there is priority and posteriority in time, as is stated in Physics 4.

Therefore, because a principle is said to be what is first in any order, and the order which is considered according to priority and posteriority in continuous quantity is first known by us (and things are named by us insofar as they are known to us), for this reason the term “principle,” properly considered, designates what is first in a continuous quantity over which motion passes. Hence he says that a principle is said to be that from which someone first moves something, that is, any part of a continuous quantity from which local motion begins.

Or, according to another reading, some part of a thing from which motion will first begin, that is, some part of a thing from which it first begins to be moved (for example, in the case of a line, and in that of any kind of journey, the principle is the point from which motion begins). But the opposite or contrary point is something different or other, namely, the end or terminus. It should also be noted that a principle of motion and a principle of time belong to this kind for the reason just given.

752. But because motion does not always begin from the starting point of a continuous quantity but from that part from which the motion of each thing begins most readily, he therefore gives a second meaning of “principle,” saying that we speak of a principle of motion in another way as that from which a thing best comes into being, that is, the point from which each thing begins to be moved most easily. He makes this clear by an example, for in the disciplines, one does not always begin to learn from something that is a beginning in an absolute sense and by nature, but from that from which one learns most readily, that is, from those things that are better known to us, even though they are sometimes more remote by their nature.

753. Now this sense of “principle” differs from the first. For in the first sense a principle of motion gets its name from the starting point of a continuous quantity, whereas here the principle of continuous quantity gets its name from the starting point of motion.

Hence in the case of those motions which are over circular continuous quantities and have no starting point, the principle is also considered to be the point from which the movable body is best or most fittingly moved according to its nature.

For example, in the case of the first thing moved, the starting point is in the east. The same thing is true in the case of our own movements; for a man does not always start to move from the beginning of a road but sometimes from the middle, or from any terminus at all from which it is convenient for him to start moving.

754. Now from the order considered in local motion we come to know the order in other motions. And for this reason we have the senses of “principle” based upon the principle of generation or coming to be of things. But this is taken in two ways; for it is either inherent, that is, intrinsic, or non-inherent, that is, extrinsic.

755. In the first way, then, “a principle” means that part of a thing which is first generated and from which the generation of the thing begins; for example, in the case of a ship the first thing to come into being is the base or keel, which is in a certain sense the foundation on which the whole superstructure of the ship is raised. And, similarly, in the case of a house the first thing that comes into being is the foundation.

And in the case of an animal the first thing that comes into being, according to some, is the heart, and according to others, the brain or some such member of the body. For an animal is distinguished from a non-animal by reason of sensation and motion.

Now the principle of motion appears to be in the heart, and sensory operations are most evident in the brain. Hence those who considered an animal from the viewpoint of motion held that the heart is the principle in the generation of an animal.

But those who considered an animal only from the viewpoint of the senses held that the brain is this principle, yet the first principle of sensation is also in the heart even though the operations of the senses are completed in the brain.

And those who considered an animal from the viewpoint of operation, or according to some of its activities, held that the organ which is naturally disposed for that operation—as the liver or some other such part—is the first part which is generated in an animal. But, according to the view of the Philosopher, the first part is the heart, because all of the soul’s powers are diffused throughout the body by means of the heart.

756. In the second way, “a principle” means that from which a thing’s process of generation begins but which is outside the thing. This is made clear in the case of three kinds of things.

The first is that of natural beings, in which the principle of generation is said to be the first thing from which motion naturally begins in those things that come about through motion, as those which come about through alteration or through some similar kind of motion—for example, a man is said to become large or white.

Or it is said to be that from which a complete change begins, as in the case of those things that are not a result of motion but come into being through mutation alone. This is evident in the case of substantial generation—for example, a child comes from its father and mother, who are its principles, and a fight comes from jeers, which stir men’s souls to quarrel.

757. The second kind in which this is made clear is human acts, whether ethical or political, in which that by whose will or intention others are moved or changed is called a principle. Thus those who hold civil, imperial, or even tyrannical power in states are said to have the principal places; for it is by their will that all things come to pass or are put into motion in states. Those men are said to have civil power who are put in command of particular offices in states, as judges and persons of this kind. Those are said to have imperial power who govern everyone without exception, as kings. And those hold tyrannical power who, through violence and disregard for law, keep royal power within their grip for their own benefit.

758. He gives as the third kind things made by art, for the arts too in a similar way are called principles of artificial things, because the motion necessary for producing an artifact begins from an art. And of these arts, the architectonic, which derive their name from the word principle, that is, those called principal arts, are said to be principles in the highest degree. For by “architectonic arts” we mean those which govern subordinate arts, as the art of the navigator governs the art of ship-building, and the military art governs the art of horsemanship.

759. Again, in likeness to the order considered in external motions, a certain order may also be observed in our apprehensions of things, and especially insofar as our act of understanding, by proceeding from principles to conclusions, bears a certain resemblance to motion. Therefore, in another way that is said to be a principle from which a thing first becomes known. For example, we say that postulates, that is, axioms and assumptions, are principles of demonstrations.

760. Causes are also said to be principles in these ways, for all causes are principles. For the motion that terminates in a thing’s being begins from some cause, although it is not designated a cause and a principle from the same point of view, as was pointed out above [750].

761. Therefore, it is (1013a17). Then he reduces all of the abovementioned senses of principle to one that is common. He says that all of the foregoing senses have something in common inasmuch as that is said to be a principle which comes first either with reference to a thing’s being (as the first part of a thing is said to be a principle), or with reference to its coming to be (as the first mover is said to be a principle), or with reference to the knowing of it.

762. But while all principles agree in the respect just mentioned, they nevertheless differ, because some are intrinsic and others extrinsic, as is clear from the above. Hence nature and element, which are intrinsic, can be principles—nature as that from which motion begins, and element as the first part in a thing’s generation. And mind, or intellect, and purpose, or a man’s intention, are said to be as extrinsic principles.

Again, a thing’s substance, that is, its form, which is its principle of being, is called an intrinsic principle, since a thing has being by its form.

Again, according to what has been said, that for the sake of which something comes to be is said to be one of its principles. For the good, which has the character of an end in the case of pursuing, and evil, which is an end in that of shunning, are principles of the knowledge and motion of many things—that is, all those which are done for the sake of some end. For in the realm of nature, in that of moral acts, and in that of artifacts, demonstrations make special use of the final cause.