In the notice that our senses take of the constant vicissitude of things, we cannot but observe, that several particular, both qualities and substances, begin to exist; and that they receive this their existence from the due application and operation of some other being. From this observation we get our ideas of cause and effect. That which produces any simple or complex idea we denote by the general name cause; and that which is produced, effect. Thus finding that in that substance which we call wax fluidity, which is a simple idea that was not in it before, is constantly produced by the application of a certain degree of heat; we call the simple idea of heat, in relation to fluidity in wax, the cause of it, and fluidity the effect. So also finding that the substance of wood, which is a certain collection of simple ideas, so called, by the application of fire is turned into another substance, called ashes, i. e. another complex idea, consisting of a collection of simple ideas, quite different from that complex idea which we call wood; we consider fire, in relation to ashes, as cause, and the ashes as effect. So that whatever is considered by us to conduce or operate to the producing any particular simple idea, or collection of simple ideas, whether substance or mode, which did not before exist, hath thereby in our minds the relation of a cause, and so is denominated by us.

Having thus, from what our senses are able to discover, in the operations of bodies on one another, got the notion of cause and effect, viz. that a cause is that which makes any other thing, either simple idea, substance or mode, begin to be: and an effect is that which had its beginning from some other thing: the mind finds no great difficulty to distinguish the several originals of things into two sorts.

First, when the thing is wholly made new, so that no part thereof did ever exist before; as when a new particle of matter doth begin to exist, in rerum natura, which had before no being, and this we call creation.

Secondly, when a thing is made up of particles, which did all of them before exist, but that very thing so constituted of pre-existing particles, which, considered all together, make up such a collection of simple ideas as had not any existence before; as this man, this egg, rose, or cherry, &c. And this, when referred to a substance, produced in the ordinary course of nature by internal principle, but set on work, and received from some external agent or cause, and working by insensible ways, which we perceive not, we call generation; when the cause is extrinsecal, and the effect produced by a sensible separation, or juxta-position of discernible parts, we call it making; and such are all artificial things. When any simple idea is produced, which was not in that subject before, we call it alteration. Thus a man is generated, a picture made, and either of them altered, when any new sensible quality or simple idea is produced in either of them, which was not there before; and the things thus made to exist, which were not there before, are effects; and those things, which operated to the existence, causes. In which, and all other causes, we may observe, that the notion of cause and effect has its rise from ideas, received by sensation, or reflection; and that this relation, how comprehensible soever, terminates at last in them. For to have the idea of cause and effect, it suffices to consider any simple idea, or substance, as beginning to exist by the operation of some other, without knowing the manner of that operation.

Time and place are also the foundations of very large relations, and all finite beings at least are concerned in them. But having already shown, in another place, how we get these ideas, it may suffice here to intimate, that most of the denominations of things, received from time, are only relations. Thus when any one says, that queen Elizabeth lived sixty-nine, and reigned forty-five years, these words import only the relation of that duration to some other, and mean no more than this, that the duration of her existence was equal to sixty-nine, and the duration of her government to forty-five annual revolutions of the sun; and so are all words, answering, how long. Again, William the Conqueror invaded England about the year 1066, which means this, that taking the duration from our Saviour’s time, till now, for one entire great length of time, it shows at what distance this invasion was from the two extremes: and so do all words of time, answering to the question, when, which show only the distance of any point of time, from the period of a longer duration, from which we measure, and to which we thereby consider it as related.

There are yet, besides those, other words of time that ordinarily are thought to stand for positive ideas, which yet will, when considered, be found to be relative, such as are young, old, &c. which include and intimate the relation any thing has to a certain length of duration, whereof we have the idea in our minds. Thus having settled in our thoughts the idea of the ordinary duration of a man to be seventy years, when we say a man is young, we mean that his age is yet but a small part of that which usually men attain to: and when we denominate him old, we mean that his duration is run out almost to the end of that which men do not usually exceed. And so it is but comparing the particular age, or duration of this or that man, to the idea of that duration which we have in our minds as ordinarily belonging to that sort of animals: which is plain, in the application of these names to other things: for a man is called young at twenty years, and very young at seven years old; but yet a horse we call old at twenty, and a dog at seven years; because in each of these we compare their age to different ideas of duration, which are settled in our minds, as belonging to these several sorts of animals, in the ordinary course of nature. But the sun and stars, though they have out-lasted several generations of men, we call not old, because we do not know what period God hath set to that sort of beings. This term belonging properly to those things, which we can observe in the ordinary course of things, by a natural decay, to come to an end in a certain period of time; and so have in our minds, as it were, a standard to which we can compare the several parts of their duration; and, by the relation they bear thereunto, call them young or old: which we cannot therefore do to a ruby or diamond, things whose usual periods we know not.

The relation also that things have to one another in their places and distances, is very obvious to observe; as above, below, a mile distant from Charing-cross, in England, and in London. But as in duration, so in extension and bulk, there are some ideas that are relative, which we signify by names that are thought positive; as great and little are truly relations. For here also having, by observation, settled in our minds the ideas of the bigness of several species of things from those we have been most accustomed to, we make them as it were the standards whereby to denominate the bulk of others. Thus we call a great apple, such a one as is bigger than the ordinary sort of those we have been used to; and a little horse, such a one as comes not up to the size of that idea, which we have in our minds, to belong ordinarily to horses: and that will be a great horse to a Welshman, which is but a little one to a Fleming; they two having, from the different breed of their countries, taken several-sized ideas to which they compare, and in relation to which they denominate their great and their little.

So likewise weak and strong are but relative denominations of power, compared to some ideas we have at that time of greater or less power. Thus when we say a weak man, we mean one that has not so much strength or power to move, as usually men have, or usually those of his size have: which is a comparing his strength to the idea we have of the usual strength of men, or men of such a size. The like, when we say the creatures are all weak things; weak, there, is but a relative term, signifying the disproportion there is in the power of God and the creatures. And so abundance of words, in ordinary speech, stand only for relations (and perhaps the greatest part) which at first sight seem to have no such signification: v. g. the ship has necessary stores. Necessary and stores are both relative words; one having a relation to the accomplishing the voyage intended, and the other to future use. All which relations, how they are confined to and terminate in ideas derived from sensation or reflection, is too obvious to need any explication.