But even further limitations are necessary in this innocent subserviency to the senses, which is only allowed in the _form_, without changing anything in the substance. Great moderation must be always used, and sometimes the end in view may be completely defeated according to the kind of knowledge and degree of conviction aimed at in imparting our views to others. There is a _scientific_ knowledge, which is based on clear conceptions and known principles; and a _popular_ knowledge, which is founded on feelings more or less developed. What may be very useful to the latter is quite possibly adverse to the former. When the object in view is to produce a strict conviction on principles, it is not sufficient to present the truth only in respect to its contents or subject; the test of the truth must at the same time be contained in the manner of its presentation. But this can mean nothing else than that not only the contents, but also the mode of stating them, must be according to the laws of thought. They must be connected in the presentation with the same strict logical sequence with which they are chained together in the reasonings of the understanding; the stability of the representation must guarantee that of the ideas. But the strict necessity with which the understanding links together reasonings and conclusions, is quite antagonistic to the freedom granted to imagination in matters of knowledge. By its very nature, the imagination strives after perceptions, that is, after complete and completely determinate representations, and is indefatigably active to represent the universal in one single case, to limit it in time and space, to make of every conception an individual, and to give a body to abstractions. Moreover, the imagination likes freedom in its combinations, and admits no other law in them than the accidental connection with time and space; for this is the only connection that remains to our representations, if we separate from them in thought all that is conception, all that binds them internally and substantially together. The understanding, following a diametrically opposite course, only occupies itself with part representations or conceptions, and its effort is directed to distinguish features in the living unity of a perception. The understanding proceeds on the same principles in putting together and taking to pieces, but it can only combine things by part representations, just as it can _separate_ them; for it only unites, _according to their inner relations_, things that first disclosed themselves in their separation.