Substance and Causality

Space, time, causality and substance are fundamental categories of knowledge. That is why a thing is defined as a substance existing somewhere in space and at a certain point of time having the power to produce changes in other things. Let us in this section try to understand what we mean by the notions of substance and causality.

Substance or Thing
(1) A substance or thing is that which is permanent in the midst of changes--that which remains essentially the same throughout all the successive changes of state which it undergoes in course of time, and sustains and holds these changes together, gives them a certain continuity, connection, and unity.

(2) A substance, regarded as a permanent entity amidst all changes, implies also the notion that it is a centre of effort, energy, and activity. For its permanence implies a continuous effort of self-assertion and self-preservation, which consists in resisting and overcoming the external forces acting upon it. By substances we mean the permanent principle of identity in the midst of change and difference. Qualities and activities exist in it.

(3) A substance has an essence and manifestations. Qualities are the manifestations of a substance. Without qualities it is a meaningless essence, just as qualities are meaningless without a substance.

(4) Things or substances have powers and capacities. They have powers of acting on other things. For instance, water can moisten the soil, fire can burn combustible things. Capacities are the passive, latent powers.

Descartes defines substance as what exits in itself and conceived by itself. For him, God is the absolute substance; mind and matter created by God are relative substances.

Causality
Cause and change are related notions. Why does a change happen? It is produced by its cause. Here we shall discuss only the notion of  causality. It shows that a cause produces an effect, and that a particular cause produces a particular effect. Cause, according to popular conception, can be thought of as a power or force which produces the effect. We are familiar with the dilemma, "Which came first, the chicken or the egg?" Here is an effort to understand the cause-effect relationship. From the very beginning, the investigation of the natural world consisted in the search for the relevant causes of a variety of natural phenomena.

Aristotle recognises four types of things that can be given in answer to a why-question:
(1) The material cause: “that out of which”, e.g., the bronze of a statue.
(2) The formal cause: “the form”, “the account of what-it-is-to-be”, e.g., the shape of a statue.
(3) The efficient cause: “the primary source of the change or rest”, e.g., the artisan, the art of bronze-casting the statue, the man who gives advice, the father of the child.
(4) The final cause: “the end, that for the sake of which a thing is done”, e.g., health is the end of walking, losing weight, purging, drugs, and surgical tools.

Causality, therefore, is the agency or efficacy that connects one process (the cause) with another process or state (the effect), where the first is understood to be partly responsible for the second, and the second is dependent on the first.