In a section of his Treatise of Human Nature that is concerned with skepticism regarding the senses, David Hume offers a defense of skepticism concerning the external world.
In the course of that discussion, Hume describes a certain philosophical view:
“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.”
Hume then goes on to claim that this philosophical view is not really satisfactory: “But however philosophical this new system may be esteemed, I assert that ’tis only a palliative remedy, and that it contains all the difficulties of the vulgar system, with some others, that are peculiar to itself.” Part of what Hume claims is that this “philosophical hypothesis” has nothing to recommend it from the point of view of reason, and his argument in support of that contention is contained in the following paragraph: “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 shows, that there is a connection 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 relation of cause and effect between different perceptions, but can never observe it between perceptions and objects. ‘Tis impossible, therefore, that from the existence of 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.”
Try to set out Hume’s argument in an explicit, step-by-step fashion. If you think that Hume’s argument is plausible, defend it against one or two important objections. If you think the argument is unsound, carefully set out what you take to be the crucial objection (or objections) to it, and defend that objection (or objections) in a detailed way.