એરિસ્ટોટલ examines the concept of substance and essence ("ousia") in his "Metaphysics", Book VII and he concludes that a particular substance is a combination of both matter and form. As he proceeds to the book VIII, he concludes that the matter of the substance is the substratum or the stuff of which it is composed, "e.g." the matter of the house are the bricks, stones, timbers etc., or whatever constitutes the "potential" house. While the form of the substance, is the "actual" house, namely 'covering for bodies and chattels' or any other differentia (see also predicables). The formula that gives the components is the account of the matter, and the formula that gives the differentia is the account of the form.

With regard to the change ("kinesis") and its causes now, as he defines in his Physics and On Generation and Corruption 319b-320a, he distinguishes the coming to be from: 1) growth and diminution, which is change in quantity; 2) locomotion, which is change in space; and 3) alteration, which is change in quality.

The coming to be is a change where nothing persists of which the resultant is a property. In that particular change he introduces the concept of potentiality ("dynamis") and actuality ("entelecheia") in association with the matter and the form.

Referring to potentiality, this is what a thing is capable of doing, or being acted upon, if it is not prevented by something else. દા.ત., the seed of a plant in the soil is potentially ("dynamei") plant, and if is not prevented by something, it will become a plant. Potentially beings can either 'act' ("poiein") or 'be acted upon' ("paschein"), which can be either innate or learned. દા.ત., the eyes possess the potentiality of sight (innate - being acted upon), while the capability of playing the flute can be possessed by learning (exercise - acting).

Actuality is the fulfillment of the end of the potentiality. Because the end ("telos") is the principle of every change, and for the sake of the end exists potentiality, therefore actuality is the end. Referring then to our previous example, we could say that actuality is when the seed of the plant becomes a plant.

" For that for the sake of which a thing is, is its principle, and the becoming is for the sake of the end; and the actuality is the end, and it is for the sake of this that the potentiality is acquired. For animals do not see in order that they may have sight, but they have sight that they may see."

In conclusion, the matter of the house is its potentiality and the form is its actuality. The formal cause ("aitia") then of that change from potential to actual house, is the reason ("logos") of the house builder and the final cause is the end, namely the house itself. Then એરિસ્ટોટલ proceeds and concludes that the actuality is prior to potentiality in formula, in time and in substantiality.

With this definition of the particular substance (i.e., matter and form), એરિસ્ટોટલ tries to solve the problem of the unity of the beings, "e.g.", what is that makes the man one? Since, according to પ્લેટો there are two Ideas: animal and biped, how then is man a unity? However, according to એરિસ્ટોટલ, the potential being (matter) and the actual one (form) are one and the same thing.

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