To take stumbling-blocks out of the reader's way has been the main object of this Chapter. It has discussed the meaning and force of several words. The discussion may have seemed somewhat intricate,--but if honest, and, so far as it goes, thorough, no one will deny its utility. For facts are known to us as words, and words are facts to our intellect, since they express our apprehension of objects. They are, in brief, the interpreters of a world-wide human consciousness. And in the strength of consciousness our knowledge stands, if it does stand;--unfaithful to consciousness, it must fall, and ought to die the death of a traitor.[40] The word most discussed has been that one upon which turns the best known argument by Natural Theology--"Design." We trust also, that it may hereafter gain additional clearness under sidelights from other trains of thought.[41] And what next follows will be essentially a discussion of thoughts and things--in which words are to be treated less as their representatives, and more as our servants and implements. For this Chapter will have been written to very little purpose if the reader has failed to perceive that Natural Theology[42] includes at the very least two distinct elements--two separate sets of premises drawn from different sources. One of these factors rests upon our human knowledge of the natural world we live in--the other requires a deeper kind of knowledge, and one far less cultivated upon inductive principles--the knowledge, that is to say, of our own nature--our essential humanity and self-ness. The investigation of this last element is of paramount importance for the purpose we have in hand, since, without some ascertained principles and conditions of truth, men may fold their hands and view all behind and above the moving diorama of present impressions as ideas sublime but hopeless[43]--too high for us, who surely can never attain to them. The plan, therefore, of this essay is to take from the point now reached a fresh start--to set out, not from a consideration of what we may desire to know, but of how much or how little can be known, and the conditions of our knowing it. An honest wish to be sure of one single thing soon shows us the impediments we meet in making quite sure of anything. Soon, also, we painfully learn that these impediments arise from _two_ persistent sets of causes. Difficulties on the one hand occasioned by the obscurity, complication, or many-sidedness of objects actually existing _in rerum naturâ_. Difficulties on the other hand, which, like barnacles and remoræ attached to a good ship's wooden bottom, act as drags and retardations on our own apprehending faculties. Barnacle-like, they can only be kept at a distance or detached by carefully-devised contrivances. And these again give rise to troubles of other kinds,--just as copper-sheathed keels or iron vessels are not without their drawbacks.