One of the problems faced by the student of philosophy or science is when a particular terminology is used that is frequently at variance with everyday language. One of the fundamental problems in the history of philosophy is the relationship between freedom and necessity, a complex question, which is not made any easier when it emerges in different disguises – causality and chance, necessity and accident, determinism and indeterminism, etc.

We all know from everyday experience what we mean by necessity. When we need to do something, it means that we have no choice. We cannot do otherwise. The dictionary defines necessity as a set of circumstances compelling something to be, or to be done, especially relating to a law of the universe, inseparable from, and directing, human life and action. The idea of physical necessity involves the notion of compulsion and constraint. It is conveyed by expressions like “to bow to necessity”. It occurs in proverbs like “necessity knows no law”.

In the philosophical sense, necessity is closely related to causality, the relation between cause and effect – a given action or event necessarily gives rise to a particular result. For example, if I stop breathing for an hour, I will die, or if I rub two sticks together, I will produce heat. This relation between cause and effect, which is confirmed by an infinite number of observations and practical experiences, plays a central role in science. By contrast, accident is regarded as an unexpected event, which occurs without apparent cause, as when we trip over a loose paving stone, or drop a cup in the kitchen. In philosophy, however, accident is a property of a thing which is a merely contingent attribute, that is, something which is not part of its essential nature. An accident is something that does not exist of necessity, and which equally well could not have happened. Let us consider an example.

If I let this piece of paper go, it will normally fall to the floor, because of the law of gravity. That is an example of causation, of necessity. But if a sudden draught should cause the paper to blow away unexpectedly, that would be generally seen as chance. Necessity is therefore governed by law, and can be scientifically expressed and predicted. Things which happen of necessity are things which could not have happened otherwise. On the other hand, random events, contingencies, are events that might, or might not, happen; they are governed by no law that can be clearly expressed and are by their very nature, unpredictable.

Experience of life convinces us that both necessity and accident exist and play a role. The history of science and society shows exactly the same thing. The whole essence of the history of science is the search for the underlying patterns of nature. We learn early in life to distinguish between the essential and non-essential, the necessary and contingent. Even when we come across exceptional conditions that may seem “irregular” to us at a given stage of our knowledge, it often turns out that subsequent experience reveals a different kind of regularity, and still deeper causal relations, which were not immediately obvious.

The search for a rational insight and understanding of the world in which we live is intimately connected with the need to discover causality. A small child, in the process of learning about the world, will always ask “why?” – to the distraction of its parents, who are frequently at a loss for an answer. On the basis of observation and experience, we formulate a hypothesis as to what causes a given phenomenon. This is the basis of all rational understanding. As a rule these hypotheses in turn give rise to predictions concerning things that have not yet been experienced. These may then be tested, either by observation or practice. This is not only a description of the history of science, but also of an important part of the mental development of every human being from early childhood on. It therefore covers intellectual development in the very broadest sense of the word, from the most basic learning processes of a child up to the most advanced study of the universe.

The existence of causality is shown by an immense number of observations. These enable us to make important predictions, not only in science, but in everyday life. Everyone knows that if water is heated to 100°C, it turns into steam. This is the basis not only for making a cup of tea, but for the industrial revolution, upon which the whole of modern society rests. Yet there are philosophers and scientists who seriously maintain that steam cannot be said to be caused by heating water. The fact that we can make predictions about a vast number of events is itself proof that causality is not merely a convenient way of describing events, but, as David Bohm points out, an inherent and essential aspect of things. Indeed, it is impossible even to define the properties of things without resorting to causality. For example, when we say that something is red, we imply that it will react in a certain way when subjected to specified conditions – i.e., a red object is defined as one which when exposed to white light will reflect mostly red light. Similarly, the fact that water becomes steam when heated, and ice when cooled, is the expression of a qualitative causal relationship which is part of the essential properties of this liquid, without which it could not be water. The general mathematical laws of motion of moving bodies are likewise essential properties of these bodies, without which they could not be what they are. Such examples may be multiplied without limit. In order to understand why and how causality is so closely bound up with the essential properties of things, it is not enough to consider things statically and in isolation. It is necessary to consider things as they are, as they have been, and as they will necessarily become in the future – that is to say, to analyse things as processes.

In order to understand particular events, it is not necessary to specify all the causes. Indeed, this is not possible. The kind of absolute determinism put forward by Laplace was answered in advance by Spinoza in the following witty passage:

For example, if a stone falls from a roof on the head of a passer-by and kills him, they will show by their method of argument that the stone was sent to fall and kill the man; for if it had not fallen on him for that end, by God’s will, how could so many circumstances (for often very many circumstances concur at the same time) concur by chance? You will reply, perhaps: ‘The wind was blowing and the man had to pass that way, and hence it happened.’ But they will retort: ‘Why was the wind blowing at that time? And why was the man going that way at that time?’ If again you reply: ‘The wind had then arisen on account of the agitation of the sea the day before, the previous weather having been calm, and the man was going that way at the invitation of a friend,’ they will again retort, for there is no end to their questioning: ‘Why was the sea agitated, and why was the man invited at that time?’

And thus they will pursue you from cause to cause until you are glad to take refuge in the will of God, that is, the asylum of ignorance. Thus again, when they see the human body they are amazed, and as they know not the cause of so much art, they conclude that it was not by mechanical art, but divine or supernatural art, and constructed in such a manner that one part does not injure another. And hence it comes about that someone who wishes to seek out the true causes of miracles, and to understand the things of nature like a man of learning, and not to stare at them in amazement like a fool, is widely deemed heretical and impious, and proclaimed such by those whom the mob adore as interpreters of nature and the Gods. For these know that once ignorance is laid aside, that wonderment which is their only means of arguing and of preserving their authority would be taken away.[11]

  1. Spinoza, Ethics, p. 8.