It appears that the relations by which things are linked together, have a great influence in directing the train of thought; and we find by experience, that objects are connected in the mind precisely as they are externally. Beginning then with things external, we find that they are not more remarkable by their inherent properties than by their various relations. We cannot any where extend our view without perceiving things connected together by certain relations. One thing perceived to be a cause, is connected with its several effects; some things are connected by contiguity in time, others by contiguity in place; some are connected by resemblance, some by contrast; some go before, some follow. Not a single thing appears solitary, and altogether devoid of connection. The only difference is, that some are intimately connected, some more slightly; some near, some at a distance. Experience as well as reason may satisfy us, that the train of mental perceptions is in a great measure regulated by the foregoing relations. Where a number of things are linked together, the idea of any one suggests the rest; and in this manner is a train of thoughts composed. Such is the law of succession; whether an original law, or whether directed by some latent principle, is doubtful; and probably will for ever remain so. This law, however, is not inviolable. It sometimes happens, though rarely, that an idea presents itself to the mind without any connection, so far at least as can be discovered. But though we have not the absolute command of ideas, yet the Will hath a considerable influence in directing the order of connected ideas. There are few things but what are connected with many others. By this means, when any thing becomes an object, whether in a direct survey, or ideally only, it generally suggests many of its connections. Among these a choice is afforded. We can insist upon one, rejecting others; and we can even insist upon what has the slightest connection. Where ideas are left to their natural course, they are generally continued through the strongest connections. The mind extends its view to a son more readily than to a servant, and more readily to a neighbour than to one living at a distance. This order may be varied by Will, but still within the limits of connected objects. In short, every train of ideas must be a chain, in which the particular ideas are linked to each other. We may vary the order of a natural train; but not so as to dissolve it altogether, by carrying on our thoughts in a loose manner without any connection. So far doth our power extend; and that power is sufficient for all useful purposes. To give us more power, would probably be detrimental instead of being salutary.