The problem as to the extent of knowledge has absorbed philosophical attention from the time of Kant, who CI d lilted that only phenomena can lie known, and that ultimate reality is unknow able. Our previous discussion should now enable us to see the fallacy of this position. It con sists in the unwarranted assumption of an ulti mate reality lying behind phenomena, an assump tion which is necessitated, as we have seen. by trying to carry too far a perfectly valid distinc tion between phenomena. BI.Iween phenomena there are differences in degree of reality in the sense that, sonic phenomena delude us into expect• ing other phenomena however, do not ap pear. while on the other hand other phenomena do not delude us. Our expectations based on their appearance are verified. The phenomena of the former kind are illusions. are 'mere appearances.' are 'intreal.' The unreality is nothing intrinsic.
It is due to mistaken inference, and when the in ference is corrected, the illusion, the unreality, disappears. The straight stick thrust into the water appears broken. To the man who knows the laws of refraction there is no unreality in the broken appearance. The break is a real break, but not in the tangible stick or in the stick as a material for any mechanical uses. The break is in the line of movement of the rays of light. The isual sense hears correct witness as to the actual occurrence in the visible, i.e. the luminous char acter of the object. The brokenness of the object as seen is part of ultimate reality, and is as absolutely and unqualifiedly and indefeasibly real as any other reality in the real universe. There are no degrees in reality in any metaphysical sense; there are degrees in knowledge of reality; i.e. the knowledge of the connections that prevail between real things, so-called illusions included.
is only in a practical sense that one phenom enon differs from another phenomenon in reality, and even in this sense with increase of knowledge there conies increase of reality. Just as the reality of a normal vision is two-fold, so the reality of an hallucination is two-fold. In normal vision the seen appearance is actually seen and also means further possible appearances, tactual and otherwise. So in hallucination the seen ap pearance is actually seen and also means, when once the laws of hallucination are known, sonic verifiable disorder in the nervous system. Neither meaning is further-fetched than the other. It is only by slowly accumulatml associations that visible appearances come to mean tangible appear ances. These associations are acquired in infancy and childhood and have become so fixed that we consider them part of the original significance of the visual sensations themselves. In the ease of
hallucinations the correct associations have to be acquired in adult life and run• counter to the normal associations. Bence we consider it straining the meaning of words to say that hallu cinations mean nervous derangement. But the meaning is just that, for the meaning of anything always itself means the known connections it has. Thus we see lhat there is no reality beyond ap pearance; appearances are themselves real and there is no valid ground for restricting the limits of the possibly knowable. Only experience can tell us what is knowable. that is, what is real; for everything real is knowable and everything knowable is real. See HEGEL; MIME; KANT: BERKELEY; GREEN, T. H.; DESCARTES; SPINOZA; LEIBNITZ; LOCKE; LOGIC; JUDGMENT.
The bibliography of epistemology includes nearly all the philosophical works of modern limes. Specially to be mentioned are: Locke, Essay Concerning Human Understanding ( 1690 ) ; Berkeley, Treatise Concerning the Principles of Human Knowledge (1710) ; Hume, Treatise of Human 2Vature (1739) ; id.. Enquiry Concerning Human Understanding (1748) ; Kant. Kritik der reinen Vermin(' (1781) : .1. G. Fichte, Wis senschaftslehre (1794) ; Hegel, Encyclopiidie der philosophischen Wisscnsehaften im Grund rissc, in Wcrke, vol. vii. (Berlin, 1847) ; id., Wissenschaft der I,ogik. vols. iii.. v. (Berlin 1841) ; Lotze. Melaphysik (Leipzig, ]879) ; id., Loqik 1874) ; id., Mikrokosmos 1856 (14) ; .John Stuart Mill, Logic. Ratiocinative and Inductive (London, 1843; 8th ed. l872) ; id., Examination of Sir Hamilton's Philos ophy (ib., 1865); Green, Introduction to Hume (ib., 1874) ; id., Prolegomena to Ethics (ib., 180) ; Bradley, Principles of Logic (ib., 1883) ; id., Appearance and Reality (2d ed., ib., 1897) ; Bosanquet, Knowledge and Reality, ( ib., 1885) ; id., Logic (ib., 1888) ; Caird, Critical Philosophy of Kant (ib., 1889) llobliouse, Theory of Knowl edge ( ib., 1896) ; Ladd, Philosophy of Knowledge (New York, 1896) ; Bowne, Theory of Thought and Knowledge (ib., 1897) ; Ward, Noturalicm and Agnosticism ( London, 1899) ; Pearson, Grammar of Selene(' ( 2d ed.. ib., 1900) ; Ormond Foundations of Knowledge (New York, 1901); Cohen, Konts Thcorie der Erfahrung (2d ed., Berlin, 1885) ; Meld, Dcr philosophische Kriti eism us (Leipzig, 1876-87) ; Schubert-Soldern, Orundlugen eine?. Erkenntnisstheoric (ib., 1884); Volkelt, Erfahrung und Denken (ib., 1886) ; Ave narius, Kritik der reinen Erfahrung (ib., 18S8 90) ; id., Der 'in enschliche Wellbegriff (ib., 1891).