Every sense perception is an actual and natural object. Truth exists in the form of natural phenomena, and whatever is, is true. Substance and attribute are only terms for certain relations. They are not contradictions, and, as a matter of fact, all contradictions disappear before our faculty of generalization and differentiation. For this faculty reconciles all contradictions by finding a general quality in all differences. Existence, or universal truth, is the general object, the raw material, of the faculty of thought. This material is of the utmost variety and supplied by the senses. The senses reveal to us the substance of the universe in the forms of concrete qualities, in other words, the nature of perceptible matter is revealed to the faculty of thought through a variety of concrete forms. It is not perceived as a general essence, but only through interdependent phenomena. Out of the interdependence of the sense perceptions with our faculty of thought there arise quantities, general concepts, things, true perceptions, or understood truths. Essence and truth are two terms for the same thing. Truth, or the essence and nature of things, is a theoretical concept. As we have seen, we receive impressions of things in two ways, viz., a sense impression and a mental impression, the one practical, the other theoretical. Practice furnishes us with the sense impression, theory with the mental nature of things. Practice is the premise of theory, sense perception the premise of the nature which is also called the truth. The same truth manifests itself in practice either simultaneously or consecutively in the same place or in different places. It exists theoretically as a homogeneous conception. Practice, phenomena, sense perceptions, are absolute qualities, that is to say they have no quantitative limitation, they are not restricted by time or space. They are absolute and infinite qualities. The qualities of a thing are as infinite as its parts. On the other hand, the work of the faculty of thought, of theory, creates at will an infinite number of quantities, and it conceives every quality of sense _perceptions_ in the form of quantities, as the essential nature of things, as truths. Every conception has a quality of some sense perception for its object. Every object can be conceived by the faculty of thought only as a quantitative unit, as true nature, as truth.