Mysteries in general are modes of the causal relation between objects in nature,—modes which are real or held to be real, but which cannot be disclosed to every man by the natural use of his powers of knowledge. Eternal truths, that is, those necessary relations of objects which are founded on the nature of our powers of knowledge, however few may be familiar with them, are not, according to this definition, mysteries, because any one can discover them by the use of his powers of knowledge.
On the other hand, the results of sympathy and antipathy, the medical specifics, and similar effects, which some men fall upon by mere accident, and which they afterwards find confirmed by means of observations and experiments, are genuine mysteries of nature, which can be made known to another person, not by the use of his powers of knowledge, but only either by an accident of the same kind, or by communication from the first discoverer. If mysteries of this sort are not confirmed by observation and experiment, the belief in their reality is called superstition.
Religion is a covenant formed between man and another moral being of a higher genus. It presupposes a natural relation between man and this higher moral being, so that, by the mutual fulfilment of their covenant, they advance the interest of each other. If this natural relation (not being merely arbitrary and conventional) is real, and the mutual obligation of the contracting persons is founded on this relation, then it forms a true, but otherwise a false, natural religion. If the mutual obligation between man and the higher being or his representatives is drawn up in a formal code, there arises a positive or revealed religion.
The true religion, natural as well as revealed, which, as already observed, constitutes Judaism, consists in a contract, at first merely understood, but afterwards expressed, between man and the Supreme Being, who revealed Himself to the patriarchs in person (in dreams and prophetic appearances), and made known by them His will, the reward of obeying it and the punishment of disobedience, regarding which a covenant was then with mutual consent concluded. Subsequently, through his representative Moses, He renewed His covenant with the Israelites in Egypt, determining more precisely their mutual obligations; and this was afterwards on both sides formally confirmed on Mount Sinai.
To the thoughtful reader I do not need to say, that the representation of a covenant between God and man is to be taken merely analogically, and not in its strict sense. The absolutely Perfect Being can reveal Himself merely as idea to the reason. What revealed itself to the patriarchs and prophets, suitably to their power of comprehension, in figure, in an anthropomorphic manner, was not the absolutely Perfect Being Himself, but a representative of Him, His sensible image. The covenant, which this Being concludes with man, has not for its end the mutual satisfaction of wants; for the Supreme Being has no wants, and the wants of man are satisfied, not by means of this covenant, but only by observation of those relations between himself and other natural objects, which are founded on the laws of nature. This covenant, therefore, can have its foundation nowhere but in the nature of reason, without reference to any end.
Heathenism, in my opinion, is distinguished from Judaism mainly by the fact, that the latter rests upon the formal, absolutely necessary laws of reason, while the former (even if it be founded on the nature of things and therefore real) rests upon the material laws of nature which are merely hypothetically necessary. From this the inevitable result is polytheism; every particular cause is personified by imagination, that is, represented as a moral being, and made a particular deity. At first this result was a matter of mere Empiricism; but by and by men had occasion to observe that these causes, which were represented as particular deities, were dependent on each other in their effects, and in a certain aspect subordinate to each other. There thus arose gradually a whole system of heathen theology, in which every deity maintains his rank, and his relation to the rest is determined.
Judaism, on the other hand, in its very origin contemplated a system, that is, a unity among the forces of nature; and thereby it received at last this pure formal unity. This unity is merely of regulative use, that is, for the complete systematic connection of all the phenomena of nature; and it presupposes a knowledge of the multiplicity of the various forces in nature. But owing to their excessive love of system, and their anxiety for the preservation of the principle in its purity, the Israelites seem to have wholly neglected its application. The result was that they preserved a religion which was pure indeed, but at the same time very unfruitful, both for the extension of knowledge and for its application in practical life. By this cause may be explained their constant murmuring against the leaders of their religion, and their repeated relapse into idolatry. They could not, like enlightened nations at the present day, direct their attention to purity of principle and useful application of their religion at the same time, and therefore of necessity they failed either in the one or in the other. Finally the Talmudists introduced a merely formal application of religion which aimed at no real end; and by this means they made matters worse and worse.
This religion, therefore, which, by the intention of its founder, should have formed the Jews into the wisest and most intelligent of nations, made them by its injudicious application the most ignorant and unreasonable of all. Instead of the knowledge of nature being combined with the knowledge of religion, and the former subordinated to the latter merely as the material to the formal, the former was altogether neglected; and the principle, maintained in its mere abstractness, continued without any application.
Mysteries of religion are objects and acts, which are adapted to ideas and principles, and the inner meaning of which is of great importance, but which have in their outward form something unseemly or ridiculous or otherwise objectionable. They must therefore, even in regard to their outward form, be kept concealed from the vulgar eye, which cannot penetrate into the inner meaning of anything; and accordingly for it they must be a double mystery. That is to say, the objects or acts themselves constitute the lesser mysteries, and their inner meaning the greater mysteries.
Of this sort, for example, among the Jews, in the tabernacle, and afterwards in the Holy of Holies in the temple, was the ark of the covenant, which, according to the testimony of renowned authors, showed much resemblance to the sacred chest in the innermost shrine of some heathen temples. Thus we find among the Egyptians the casket of Apis, that concealed from the vulgar eye this dead animal, which as a symbol indeed had an important meaning, but in itself presented a repulsive aspect. The ark of the covenant in the first temple contained, it is true, according to the testimony of Holy Scripture, nothing besides the two tables of the law; but of the ark in the second temple, built after the Babylonian captivity, I find in the Talmud a passage which is too remarkable not to be adduced. According to this passage the enemies, who seized the temple, found in the Holy of Holies the likeness of two persons of different sex embracing, and profaned the sacred object by a crass exposition of its inner meaning. This likeness was said to be a vivid sensible representation of the union between the nation and God, and, in order to guard against abuse, had to be withdrawn from the eye of the common people, who cling to the symbol, but do not penetrate to its inner meaning. For the same reason the cherubim also were concealed behind the veil.