"1. Metaphysical topics suppose that the soul is immaterial, and that 'tis impossible for thought to belong to a material substance.[39] But just metaphysics teach us that the notion of substance is wholly confused and imperfect; and that we have no other idea of any substance, than as an aggregate of particular qualities inhering in an unknown something. Matter, therefore, and spirit, are at bottom equally unknown, and we cannot determine what qualities inhere in the one or in the other.[40] They likewise teach us, that nothing can be decided _a priori_ concerning any cause or effect; and that experience, being the only source of our judgments of this nature, we cannot know from any other principle, whether matter, by its structure or arrangement, may not be the cause of thought. Abstract reasonings cannot decide any question of fact or existence. But admitting a spiritual substance to be dispersed throughout the universe, like the ethereal fire of the Stoics, and to be the only inherent subject of thought, we have reason to conclude from _analogy_, that nature uses it after the manner she does the other substance, _matter_. She employs it as a kind of paste or clay; modifies it into a variety of forms or existences; dissolves after a time each modification, and from its substance erects a new form. As the same material substance may successively compose the bodies of all animals, the same spiritual substance may compose their minds: Their consciousness, or that system of thought which they formed during life, may be continually dissolved by death, and nothing interests them in the new modification. The most positive assertors of the mortality of the soul never denied the immortality of its substance; and that an immaterial substance, as well as a material, may lose its memory or consciousness, appears in part from experience, if the soul be immaterial. Seasoning from the common course of nature, and without supposing any new interposition of the Supreme Cause, which ought always to be excluded from philosophy, _what is incorruptible must also be ingenerable_. The soul, therefore, if immortal, existed before our birth, and if the former existence noways concerned us, neither will the latter. Animals undoubtedly feel, think, love, hate, will, and even reason, though in a more imperfect manner than men: Are their souls also immaterial and immortal?"[41] Hume next proceeds to consider the moral arguments, and chiefly " ... those derived from the justice of God, which is supposed to be further interested in the future punishment of the vicious and reward of the virtuous."