Having published his Gesch. der Aesthetik in Deutschland (1868), Lotze proposed to give a systematic exposition of his phil osophy. His Drei Bucher der Logik appeared in 1874 (Eng. trs. 1888) and his Drei Bucher der Metaphysik in 1879 (Eng. trs. 1887), but the third volume which was to include aesthetics, ethics and the philosophy of religion was terminated by the death of Lotze at Berlin on July 1, 1881, three months after he had been called from Gottingen.
In his exposition of logic he established two points, viz., the existence in our mind of certain laws and forms according to which we connect the material supplied by our senses, and, secondly, the fact that logical thought cannot be usefully em ployed without the assumption of a further set of connections, not logically necessary, but assumed to exist between the data of experience and observation. These connections handed to us by the sciences and by general culture are represented by such concepts as those of cause and effect, matter and force, end and means, freedom and necessity. It is the business of philosophy firstly to investigate these concepts and to discover the grounds on which the interconnection of phenomena rests, and secondly, to present the departments of knowledge in their true proportion. It follows, then, that any idealistic philosophy must have a realistic basis. Indeed, thought could not constitute reality because it is subjective and represents externals only in adequately, and because it is only one function among others upon which it is dependent e.g., sensation, feeling and volition. All philosophical investigation falls into three parts, the first deals with those necessary forms in which we are obliged to think about things (metaphysics), the second is devoted to facts, and to the application of the results of metaphysics to these, especially to external and mental phenomena (cosmology and psychology), the third is concerned with those standards of value involved in our aesthetical or ethical judgments. We have already mentioned the final conception in which Lotze's speculation culminates, that of a personal Deity, Himself the essence of all that merits ex istence for its own sake, who in the creation and government of a world has voluntarily chosen certain laws through which His ends are to be realized. According to this view nothing is real but the living spirit of God and the world of living spirits which He has created; the things of this world have reality only in so far as they are the appearance of spiritual substance, which underlies everything.
In his metaphysical treatises, Lotze maintains that the course of things and their connection is only thinkable on the assumption of a plurality of existences, the reality of which can be conceived only as a multitude of relations. The nature of this reality can not be represented as an unalterable something, but only as a fixed order of recurrence of continually changing events or impres sions. Every attempt to think clearly what these relations are,
what we really mean, if we talk of a fixed order of events, forces upon us the necessity of thinking also that the different things which stand in relations or the different phases which follow each other cannot be merely strung together or moved by some in definable external power, in the form of some predestination or inexorable fate. The things themselves which exist and their changing phases must stand in some internal connection; they themselves must be capable of doing or suffering.
The simplest case of reciprocal action presupposes a universal substance, the essence of which we conceive as a system of laws underlying everything but known to us only through the impres sions it produces on us, which we call things. Reflection teaches us that the nature of this universal substance can only be imagined as something analogous to our own mental life, where alone we experience the unity of a self preserved in the multitude of its (mental) states. Only where such mental life appears need we assign an independent existence ; the purposes of everyday life as well as those of science are equally served if we deprive material things of an independence, and assign to them merely a connected existence through the universal substance by the action of which alone they appear to us.
The universal substance is at this stage of our investigations not endowed with the attributes of a personal Deity, and though Lotze's remarks on the subject are incomplete, in various pas sages he indicates that the absolute Being must be personal be cause personality alone possesses independence. In saying that the richness with which the working of the prime Being takes place determines the nature of existences. Lotze passes into his favourite realm of aesthetics.
Though Lotze disclaims being a follower of Herbart, his formal definition of philosophy and his conception of the object of meta physics are similar to those of Herbart, and he forms with him an opposition to the philosophies of Fichte, Schelling and Hegel, which aimed at objective and absolute knowledge, and also to the criticism of Kant, which aimed at determining the validity of all human knowledge. But Lotze's spirit is more akin to the idealistic school than to the cold formalism of Herbart. What, however, with the idealists was an object of thought alone, the absolute, is to Lotze only inadequately definable in rigorous philosophical language ; the aspirations of the human heart, the contents of our feelings and desires, the aims of art and the tenets of re ligious faith must be grasped in order to fill the empty idea of the absolute with meaning. This conviction of the emptiness of abstract notions, and of the fulness of individual life, has enabled Lotze to combine the two courses into which German philosophical thought had been moving since the death of Leibnitz.