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less vividness. Kant repudiates this more extreme
scepticism and adopts, at least in the second edition of
his chief work, a form of dualism based on the distinc-
tion of phenomena and noumena. The mind immedi-
ately perceives only its own representations. These
are modified by innate mental forms. They present
to us only phenomena. But the noumena, the things-
in-themselves, the external causes of these phenom-
enal representations, are beyond our power of cogni-
tion. Fichte rejected things-in-themselves outside
the mind, and reduced the Kantian dualism to idealis-
tic monism. The strongest and most consistent de-
fenders of dualism in modern philosophy have been
the Scotch School, including Reid, Stuart, and Hamil-
ton. .\mong English writers in more recent times
Martineau, McCosh, Mivart, and Case have carried on
the same tradition on similar lines.
The problem of dualism, as its history suggests, in- volves two main questions: (1) Does there exist a material world outside of our minds and independent of our thought? (2) Supposing such a world to exist, how does the mind attain to the cognition of it? — The former question belongs to episteraology, material logic, or general philosophy; the latter to psychol- ogy. It is tnie that dualism is ultimately rejected by the materialist who reduces conscious states to func- tions or "aspects" of the brain; but objections from this standpoint will be more suitably dealt with under materialism and monism. The idealist theory since Berkeley, in all its forms, maintains that the mind can only know its own states or representations, and that what we suppose to be an independent material world is, in the last analysis, only a series of ideas and sensa- tions plus belief in the possibility of other sensations. Our conviction of the objective reality of a vivid con- sistent dream is analogous to our conviction of the validity of our waking experience. Dualism affirms, in opposition to all forms of idealism, the independent extramental reality of the material world. Among its chief arguments are the following: (1) Our belief in the existence of other mirds is an inference from their bodies. Consequently the denial of an external mate- rial world involves the rejection of all evidence for the existence of other minds, and lands the idealist in the position of "Solipsism". (2) Phj'sical science as- sumes the existence of a material world, existing when unperceived, possessing various properties, and exert- ing various powers according to definite constant laws. Thus astronomy describes the movements of heavenly bodies moving in space of three dimensions, attracting each other with forces inversely propor- tioned to the square of the distance. It postulates the movement and action of such bodies when they are in- visible as well as when they are visible through long periods of time and over vast areas of space. From these assumptions it deduces future positions and foretells eclipses and transits many j^ears ahead. Observations carried out by subsequent generations verify the predictions. Were there not an extra- mental world whose parts exist and act in a space and time truly mirrored by our cognitions and ideas, such a result would be impossible. The branches of sci- ence dealing with sound, light, heat, and electricity are equally irreconcilable with idealism. (3) The teachings of physiology and psycho-physics become peculiarly absurd in the idealist theory. What, for instance, is meant by saying that memory is depend- ent on modifications in the nervous substance of the brain, if all the material world, including the brain, is but a collection of mental states? (4) Psychology similarly a.ssumes the extramental reality of the hu- man body in its account of the growth of the senses and the development of perception. Were the ideal- ist hypothesis true its language would be meaningless. All branches of science thus presuppose and confirm the dualistic view of common sense.
Granted, then, the truth of dualism, the psychologi-
cal question emerges: How does the mind come to
know the material world? — Broadly speaking there
are two answers. According to one the mind immedi-
ately perceives only its own representations or ideas
and from these it infers external material objects as
the cause of these ideas. According to the other, in
some of its acts it immediately perceives extended ob-
jects or part of the material world. As Hamilton
says: "What we directly apprehend is the Non-ego,
not some modification of the Ego". The theory
which maintains an immediate perception of the non-
ego he calls natural dualism or natural realism. The
other, which holds a mediate cognition of the non-ego,
as the inferred cause of a representation immediately
apprehended, he terms hypotlietical dualism or hy-
pothetical realism. The doctrine of immediate or
presentative perception is that adopted by the great
body of the Scholastic philosophers and is embodied
in the dictum that the idea, concept, or mental act of
apprehension is non id quod perdpitur sed medium quo
res percipitur — not that which is perceived but the
medium by which the object itself is perceived. This
seems to be the only account of the nature of knowl-
edge that does not lead logically to idealism; and the
history of the subject confirms this view. But affir-
mation of the mind's capacity for immediate percep-
tion of the non-ego and insistence on the distinction
between id quod and id quo percipitur, do not dispose
of the whole difficulty. Modern psychology has be-
come genetic. Its interest centres in tracing the
growth and development of cognition from the sim-
plest and most elementaiy sensations of infancy.
Analysis of the perceptive processes of a later age, e. g.
apprehension of size, shape, solidity, distance, and
other qualities of remote objects, proves that opera-
tions seemingly instantaneous and immediate may in-
volve the activity of memory, imagination, judgment,
reasoning, and sub-conscious contributions from the
past experience of other senses. There is thus much
that is indirect and inferential in nearly all the percipi-
ent acts of mature life. This should be frankly ad-
mitted by the defender of natural dualism, and the
chief psychological problem for him at the present day
is to sift and discriminate what is immediate and di-
rect from what is mediate or representative in the
admittedly complex cognitional operations of normal
adult life.
Im F.wour of Natural Dualism: — Rickaby, First Princi- ples of Knowledge (New York and London, 1901); Case, Physi- cal Realism (New York and London, 1881); Ueberweg, Logic, tr. (London, 1871); Hamilton', Metaphysics (Edinburgh and London, 1877); McCosh, Exam, of Mill (New Y'ork, 1875); Martineau, A Study of Religion (Oxford, 1888); Mivart, A^a- lure and Thought (London, 1882); Maker, Psychology (New Y'ork and London, 1908); Farges, L'Objectivite de la Percep- tion (Paris, 1891).
Against Natural Dualism: — Berkeley. Principles of Hu- man Knowledge, ed. Fraser (Oxford. 1871); ed. Krauth (Phil- adelpliia, 1874); Mill, An Exam, of Sir W. Hamilton (London, 1865); Bradley, AppearaTUX and Reality (New Y'ork and Lon- don, 1899).
Michael Maker.
Dublin (Ddblinum), Archdiocese of (Dublinen- sis), occupies about sixty miles of the middle eastern coast of Ireland, and penetrates inland about forty-six miles, including all the County of Dublin, nearly all of Wicklow, and parts of Kildare and Wexford, with three suffragans: Kildare and Leighlin, Ferns, and Ossory. It covers an area of 698,277 statute acres.
Ptolemy, who flourished in the first half of the sec- ond century, on his famous map places Eblana civitas under the same parallel of latitude as the present city of Dublin. The first mention of Duihhlinn in any extant Irish chronicles is found in the " .\nnals of the Four Masters", under date of 291, where the name, which in English signifies a black pool, is quoted as that of a river on the bank of which a battle was fought by the King of Ireland against the Leinsterinen. A river still empties into the Liffey at Dublin, now known as the Poddle River, but formerly designated the Pool
