PROP. I.————
us is excluded from our knowledge, but it is not excluded from our ignorance. In regard to this (the simply unknowable), there is no middle—a third alternative is excluded. We do not know it, and therefore we must be ignorant of it. Here the law applies; but the absolutely unknowable is excluded from our knowledge; and it is excluded equally from our ignorance. In regard to this, there is nothing but a third or middle alternative. We can neither know it, nor be ignorant of it. Here the law does not apply. Hence there is a middle between knowledge and ignorance; a middle which is excluded alike from our knowledge and from our ignorance, and this middle is the contradictory, or that which the laws of all reason prevent from being known on any terms by any intelligence. The counter-proposition, therefore, which lays down the law of excluded middle without any qualification, and denies that it is subject to any limitation, is erroneous.
The want of a clear doctrine of the contradictory has been the cause of much error in philosophy.10. One of the principal retarding causes of philosophy has been the want of a clear and developed doctrine of the contradictory. This desideratum could not be supplied so long as philosophers refused, as they have hitherto done, to found speculative science upon reason, and to carry it out from beginning to end, as a concatenated system of necessary truths. To this cause the error which we have just been considering, and many
