For it is not alone nature around him that he (Man) must explain, — he himself must be explained together with it; he is part and parcel of nature, and to search himself is a task which he cannot avoid. But man becomes the greatest enigma even to himself, the more he reflects upon himself. It is true, it has been essayed to connect man very closely with similar beings; species of apes have been spoken of that are but very little different from man. It has been said, there are some species of apes appearing as sunk in profound sadness, as pervaded by a longing desire to be freed from that narrowed confinement; ’tis a contemplative sentiment that man attributes — merely attributes, indeed!— to the soul of an animal, when he regards and represents animal stupor as profound sadness. The distance between the most perfect animals and man himself will remain a gap that can never be filled. To draw a parallel, even only very distantly, between man who, despite his inconsiderable bodily strength, notwithstanding he is greatly inferior, with regard to corporeal attributes, to other animals which are more powerful and more adroit, has nevertheless become the lord of the earth, of the whole creation, who more and more subjects to himself everything in inanimate and animate nature; who accommodates himself to, and controls all places, conditions and circumstances: to draw even the most distant comparison between man and any one animal that lives secluded — remains fixed in the same state, is limited to a certain part of the world; that, without exercising the least influence upon the rest of creation, dies away and leaves no trace behind — such a comparison, it must be confessed, looks like the reasoning of a child that fondles — then throws away and destroys its own little mimic toys! No, man is of an entirely different genus. Man, who is bound to time and space like all other corporeal and earthly creatures; individual man, who is tied to a certain extent of soil, moves within a small particle of time, nevertheless, on the other hand, conquers time and space within him, can transpose himself into the most distant regions, can place the past before him, pre-suppose the future, has a conception of what is beyond the present. Such faculty cannot be the attribute of the body; the body is circumscribed by space and time, — nothing can proceed therefrom that conquers space and time. Let us pronounce the word which would not exist if the thing did not exist: it is the Spirit. Man has a spirit, a faculty within him which is connected with his body in so far as it moves, animates him, but which is still far more, because it impels him towards rational contemplation, opens for him an insight into objects which his physical vision is unable to perceive or to attract… For language, the most faithful reflector of the spirit, constitutes the connecting link between man’s inmost thoughts and the outer world ; language most decidedly distinguishes him from all other created beings — language, born, as it were, from inward clearness, renders, in its turn, thought intelligible, and gives it full and entire clearness… How ever far a single man may progress, he will nevertheless remain merely a part of mankind, mankind itself only a part of creation, and creation, in its turn, is but the work of a greater, higher Spirit.
-Abraham Geiger, Judaism and its History, Lecture I: Of the Nature of Religion, pp. 10-14