I am trying to understand the physical concept of friction in terms of Aristotle's efficient cause. This is not a physics question.

Friction is said to be caused by the electromagnetic force between the surface molecules of two objects. But it is also said to be caused by the force exerted by asperities of the two surfaces on each other. (An asperity can be defined as follows: when you zoom into a surface, no matter how smooth, at the molecular level there are tiny prominences on the surface because it is not perfectly smooth at the molecular level, and these prominences are called asperities.)

When the asperities of two objects are attracted due to close contact, when you try to push one of them away from the other it takes a bit of force to disconnect their attraction. This attraction is what causes friction.

After reading this description of friction I got a bit confused. Is the efficient cause of friction the electromagnetic force or the force between the asperities? I am aware that they are basically the same thing: the electromagnetic force is what causes the force between the asperities on the surfaces of the two objects.

However, what I am unsure about is how I would answer a question such as, "What is the efficient cause of friction between two objects?" Should I say "it is caused by the electromagnetic force between their surface molecules", or "it is caused by the electromagnetic force between the asperities on the surfaces" or "it is caused by the force between the asperities on the surfaces" (omitting "electromagnetic")?

I think my question is more about: How do I achieve crystal clarity when asking and answering questions, so that the answer exactly answers the question? There seem to be many different ways of answering the same question.

Is there a method for removing this ambiguity by wording the question differently?

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    Friction is a single word covering many effects from.pauli exclusion principle to van der walls forces. to answer the qiestion of what causes friction in particular instances one would have to study those cases.
    – Richard
    Mar 19 '19 at 11:55
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    This sounds more like a question pertaining to Physics — which is way more efficient in describing natural phenomenons —, but ultimately pertaining to English since you are trying to express two specific ideas without being exclusive of either.
    – user31740
    Mar 19 '19 at 12:26
  • A scientific explanation according to Aristotle needs all four causes one of which is the efficient one : "the primary source of the change or rest”. See also the example of explanation of a natural phenomenon. Mar 19 '19 at 15:42
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    See Phys, 289a13-a34: "Movement tends to create fire in wood, stone, and iron; and with even more reason should it have that effect on air, a substance which is closer to fire than these. An example is that of missiles, which as they move are themselves fired so strongly that leaden balls are melted; and if they are fired the surrounding air must be similarly affected. Now while the missiles are heated by reason of their motion in air, which is turned into fire by the agitation produced by their movement". The cause of heating due to friction is the "agitation" of particles due to motion. Mar 19 '19 at 15:48
  • "Is there a method for removing this ambiguity by wording the question differently?" Yes and no. The reason for the possibility of multiple answers is that there are multiple frameworks/schemes one can adopt for answering them, e.g. of electromagnetic fields, or of quantum mechanics, or of asperities,... for friction. One can reduce the ambiguity about the answer by specifying a particular scheme, but there is no removing plurality of schemes suitable for answering the question. Aristotle's idea of one "right" scheme that "carves nature at the joints" was natural, but too naive.
    – Conifold
    Mar 19 '19 at 18:56

Q. What is the efficient cause of friction between two objects?

A. The efficient cause of friction between two objects is that which sustains both objects in their movement from potence to actuality, in order that they may interact with each other to produce friction.

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