If this be the law on the subject, (and we conceive that it must be so ruled) it settles the question as to the _second_ mode of dealing with the problem of perception. It establishes the point that this method of treating the problem is not to be permitted. It is _tabooed_ by the very nature of things. Air and sunshine are excellent and most important articles, but they are not things to carry to market in bottles,--because no labour is required to produce them, and because they are the gratuitous and abundant property of every living soul. In the same way, the existence of a material universe--and the fact that we believe in its existence--these are most important truths; but they are not things to take to market in books, and for a like reason. They are important things to _know_, but they are not important things to _tell_. We conceive, in short, that Nature, by rendering these and similar truths unreservedly patent to the whole human race, has affixed to them her own contraband,--interdicting their communication; and that Dr Reid, in making them the staple of his publications, was fighting against an eternal law. He undertook to teach the world certain truths connected with perception, which by his own admission the world already knew just as well as he did--and which required no labour for their production. This way of going to work with any problem, is certainly not the best. These remarks settle, we think, the general pretensions of the philosophy of Common Sense. In justice, however, to this philosophy, we must not omit to mention, that Sir William Hamilton has adduced the evidence of no less than one hundred and six witnesses, whose testimony goes to establish that it is a [Greek: ktema es aei]--a perpetual possession, "a _joy_ for ever." The _first_ and _third_ modes of dealing with our problem remain to be considered. The first mode ignores the problem altogether, it refuses to have any thing to do with it. Perhaps this mode is the best of the three. We will not say that it is not: it is at any rate preferable to the second. But once admit that philosophy is a legitimate occupation, and this mode must be set aside, for it is a negation of all philosophy. Every thing depends upon this admission. But the admission is, we conceive, a point which has been already, and long ago decided. Men must and will philosophise. That being the case, the only alternative left is, that we should discuss the highest problem of philosophy in the terms of the _third_ mode proposed. We have called this the speculative method--which means nothing more than that we should expend upon the investigation the uttermost toil and application of thought; and that we should estimate the truths which we arrive at, not by the scale of their importance, but by the scale of their difficulty of attainment,--of their cost of production. _Labour_, we repeat it, is the standard which measures the value of truth, as well as the value of wealth.