the disposition of our nerves and animal spirits.  This opinion is confirmed by the seeming encrease and diminution of objects, according to their distance; by the apparent alterations in their figure; by the changes in their colour and other qualities from our sickness and distempers:  and by an infinite number of other experiments of the same kind; from all which we learn, that our sensible perceptions are not possest of any distinct or independent existence.

The natural consequence of this reasoning should be, that our perceptions have no more a continued than an independent existence; and indeed philosophers have so far run into this opinion, that they change their system, and distinguish, (as we shall do for the future) betwixt perceptions and objects, of which the former are supposed to be interrupted, and perishing, and different at every different return; the latter to be uninterrupted, and to preserve a continued existence and identity.  But however philosophical this new system may be esteemed, I assert that it is only a palliative remedy, and that it contains all the difficulties of the vulgar system, with some others, that are peculiar to itself.  There are no principles either of the understanding or fancy, which lead us directly to embrace this opinion of the double existence of perceptions and objects, nor can we arrive at it but by passing through the common hypothesis of the identity and continuance of our interrupted perceptions.  Were we not first perswaded, that our perceptions are our only objects, and continue to exist even when they no longer make their appearance to the senses, we should never be led to think, that our perceptions and objects are different, and that our objects alone preserve a continued existence.  The latter hypothesis has no primary recommendation either to reason or the imagination, but acquires all its influence on the imagination from the former.  This proposition contains two parts, which we shall endeavour to prove as distinctly and clearly, as such abstruse subjects will permit.

As to the first part of the proposition, that this philosophical hypothesis has no primary recommendation, either to reason, or the imagination, we may soon satisfy ourselves with regard to reason by the following reflections.  The only existences, of which we are certain, are perceptions, which being immediately present to us by consciousness, command our strongest assent, and are the first foundation of all our conclusions.  The only conclusion we can draw from the existence of one thing to that of another, is by means of the relation of cause and effect, which shews, that there is a connexion betwixt them, and that the existence of one is dependent on that of the other.  The idea of this relation is derived from past experience, by which we find, that two beings are constantly conjoined together, and are always present at once to the mind.  But as no beings are ever present to the mind but perceptions; it follows that we may observe a conjunction or a relation of cause and effect between different perceptions, but can never observe it between perceptions and objects.  It is impossible, therefore, that from the existence or any of the qualities of the former, we can ever form any conclusion concerning the existence of the latter, or ever satisfy our reason in this particular.