The admission made in the last paragraph has cleared the way for the introduction of a question, from which the subject under discussion derives its principal interest, and which it is indispensable therefore carefully, though briefly, to examine. If there be certain determinate lines of conduct which men will infallibly pursue throughout all succeeding generations, how can men be free agents? How--for it is merely the old puzzle over again--how can foreknowledge be reconciled with freewill? The difficulty is not to be got rid of by discrediting the reality of freewill, and treating it as a thing for which there is no evidence. When Johnson silenced Boswell's chatter with the words, 'Sir, we know our will is free and there's an end on't,' he expressed a great truth in language not the less philosophically accurate on account of its colloquial curtness. The consciousness possessed by an agent about to perform an act, that he is at liberty to perform it or not, is really conclusive evidence that the act is free. For it matters not a jot whether consciousness be 'an independent faculty,' or whether--as, Mr. Buckle reminds us, 'is the opinion of some of the ablest thinkers'--it be not merely 'a state or condition of the mind.' If consciousness be a condition of the mind, so also is perception; but perception, whatever else it be, is also that which makes us acquainted with external phenomena, just as consciousness is that which makes us acquainted with internal emotions. The two informants, it is true, are not equally trustworthy. Perception often deceives us, but consciousness, never. We often fancy we perceive what we do not perceive. We may fancy we see a ghost, when we are merely mocked by an optical illusion, or we may mistake the impalpable imagery of the Fata Morgana for solid objects, or the rumbling of a cart for thunder. But consciousness is infallible. We cannot fancy we experience an emotion which we do not experience. We cannot fancy we are glad when we are not glad, or sorry when we are not sorry, or hopeful when in despair; and to pretend that we can possibly be conscious of willing when we are not willing, would be as absurd as to meet the _cogito, ergo sum_ of Descartes, with the reply that, perhaps, we do not really think, but only think we think.