The last two orthodox systems of philosophy, the Vaiçeshika and the Nyaya, form a closely-connected pair, since a strict classification of ideas, as well as the explanation of the origin of the world from atoms, is common to both. Much the older of the two is the Vaiçeshika, which is already assailed in the Brahma-sutras. It is there described as undeserving of attention, because it had no adherents. This was certainly not the case in later times, when this system became very popular. It received its name from the category of "particularity" (viçesha) on which great stress is laid in its theory of atoms. The memory of its founder is only preserved in his nickname Kanada (also Kanabhuj or Kana-bhaksha), which means "atom-eater." The main importance of the system lies in the logical categories which it set up and under which it classed all phenomena. The six which it originally set up are substance, quality, motion, generality, particularity, and inherence. They are rigorously defined and further subdivided. The most interesting is that of inherence or inseparable connection (samavaya), which, being clearly distinguished from that of accident or separable connection (samyoga), is described as the relation between a thing and its properties, the whole and its parts, genus and species, motion and the object in motion. Later was added a seventh, that of non-existence (abhava), which, by affording special facilities for the display of subtlety, has had a momentous influence on Indian logic. This category was further subdivided into prior and posterior non-existence (which we should respectively call future and past existence), mutual non-existence (as between a jar and cloth), and absolute non-existence (as fire in water). Though largely concerned with these categories, the Vaiçeshika system aimed at attaining a comprehensive philosophic view in connection with them. Thus while dealing with the category of "substance," it develops its theory of the origin of the world from atoms. The consideration of the category of "quality" similarly leads to its treatment of psychology, which is remarkable and has analogies with that of the Sankhya. Soul is here regarded as without beginning or end, and all-pervading, subject to the limitations of neither time nor space. Intimately connected with soul is "mind" (manas), the internal organ of thought, which alone enables the soul to know not only external objects but its own qualities. As this organ is, in contrast with soul, an atom, it can only comprehend a single object at any given moment. This is the explanation why the soul cannot be conscious of all objects simultaneously.