We see, also, that unlimited duration is an absurdity; that duration must be limited; and that self-existence involves existence out of all relation to duration. Mr. Spencer then turns to the nature of the Universe, and says: "We find ourselves on the one hand obliged to make certain assumptions, and yet, on the other hand, we find these assumptions cannot be represented in thought." Upon this it may be remarked: 1. What are here called assumptions are properly assertions, which man makes, and cannot help making, except he deny himself;--necessary convictions, first truths, first principles, _a priori_ ideas. They are organic, and so are the foundation of all knowledge. They are not results learned from lessons, but are _primary_, and conditional to an ability to learn. But supposing them to be assumptions, having, at most, no more groundwork than a vague guess, there devolves a labor which Mr. Spencer and his coadjutors have never attempted, and which, we are persuaded, they would find the most difficult of all, viz., to account for the fact of these assumptions. For the question is pertinent and urgent; 2. How came these assumptions to suggest themselves? Where, for instance, did the notion of self come from? Analyze the rocks, study plants and their growth, become familiar with animals and their habits, or exhaust the Sense in an examination of man, and one can find no notion of self. Yet the notion is, and is peculiar to man. How does it arise? Is it "created by the slow action of natural causes?" How comes it to belong, then, to the rudest aboriginal equally with the most civilized and cultivated? Was it "created" from nothing or from something? If from something, how came that something to be? We might ask, Does not the presentation of any phenomenon involve the actuality of a somewhat, in which that phenomenon inheres, and of a receptivity by which it is appreciated? Does not the fact of this assumption, as a mental phenomenon, involve the higher fact of some mental ground, some form, some capacity, which is both organic to the mind, and organized in the mind, in accordance with which the assumption is, and which determines what it must be? Or are we to believe that these assumptions are mere happenings, without law, and for which no reason can be assigned? Again we press the question, How came these assumptions to suggest themselves? 3. "These assumptions cannot be represented in thought." If "thought" is restricted to that mental operation of the Understanding by which it generalizes in accordance with the Sense, the statement is true. But if it is meant, as seems to be implied, that the notions expressed in these assumptions are not, cannot be, clearly and definitely known at all by the mind, then it is directly contrary to the truth. The ideas presented by the phrases are, as was seen above, clear and definite.