INDUCTION
782
INDUCTION
we take it partially or fully in a given case, the ques-
tion still remains: What is our ultimate rational justi-
fication for extending it at all beyond the limits of
our actual personal experience? The answers given
to this question by logicians, as indeed their entire
expositions of the niductive process, are as divergent
and conflicting as their general philosophical views
regarding the ultimate nature of the universe and of
all reality. The fact to be explained and justified is
that we believe the world outside our personal expe-
rience to be of a piece with the world within our
experience. But the Empirical or Positivist philos-
ophy, represented by Hume and Mill, makes all
rational justification of this belief impossible; for it
there is no world outside experience; it reduces all
reality in ultimate analysis to the present actual
sensations of the individual's consciousness; and the
alleging of mere custom, mere actual experience of
uniformity, as a reason for belief in unexperienced
uniformity, it regards not as a rational expectation
based on a reasoned view about the nature of reality,
but simply a blind leap in the dark. The explan-
ation of the current Monistic Idealism, which would
identify the laws of physical phenomena with the
laws of logical thought and reduce all reality to one
system of intellectually necessary thought-relations,
is no less unsatisfactory, for it confounds the
phenomena of existing, contingent being with the
metaphysical relations between abstract, possible
essences — relations which have their ultmate basis
only in the nature of the Necessary Being, God Himself.
The answer of scholastic philosophy is that the ulti-
mate rational justification for our belief in the uni-
formity of nature is our reasoned conviction that
nature is the work of an All-Wise Creator and Con-
server, Who has endowed physical agencies with
regular constant modes of activity with which He will
not interfere unless by way of miracle for motives of
the higher or moral order. The certitude of our
belief in the princi|)le and its applications is thus
hypothetical, physical, not absolute, not metaphy-
sical: " If God continues to conserve and concur with
created physical agencies, if He does not miraculously
interfere with them, if no other unknown cause inter-
vene, then those agencies will continue to act uni-
formly."
Physical induction sometimes inquires into the constitutive ("formal" and "material") causes of phenomena (as, for instance, in chemical and physical researches into the constitution of matter), some- times into their purpose (or "final" causes, as in the biological sciences) ; but mainly into their proximate efficient causes, i. e. the total group of proximate agencies sufficient and indispensable for the produc- tion of any given phenomenon. To these primarily is inductive research restricted, for the agencies oper- ative in the physical universe are .so intimately inter- woven and interdependent that, were we to trace the chains of causality outward and backward from any effect indefinitely, we should see that in a sense all the agencies in the universe are in some remote way operative in the production of any single effect. Much controversy has been needlessly imported into Logic regarding the concept of cau.se. The rejection of "clficiency" or "positive influence" from this concept and the substitution of "invariable and unconditional sequence " is a feature of Empiricism. But it can have no influence on inductive generalization about the con- duct of phenomena in space and time. For reliable generalization about the latter the only objective con- dition needed is uniformity or regularity of occurrence. The scope of induction will, however, be unduly and unjustifiably narrowed if liy physical cause we are always to understand with Mill something which is itself a phenomenon, perceptilale by the senses, and if we are to eschew all inquiry into causes which are not themselves sense-phenomena but active qualities
rooted in the natures of things and discernible only
by intellectual rea-soning. No doubt it is to induc-
tive research for mere phenomenal antecedents — for
material masses and energies — and to their exact
mathematical measurement in terms of mechanical
work that the applied sciences owe their greatest
triumphs. But though the only concern of the en-
gineer is to know how to secure useful coexistences
and .sequences of material masses and motions, yet the
man of thought, be he physical scientist or philoso-
pher, will rightly resent being prohiljited by Posi-
tivism from prosecuting a further investigation into
the rational why and wherefore of these occurrences,
into the natures and properties which reason alone
can discover through those phenomena. Men will ever
and rightly insist on inquiring inductively after
veriv cauMv, which, though they produce effects per-
ceptible by the senses, are not themselves phenomena.
However, when we push back our inquiry into the
more remote conditions, causes, .origin, and constitu-
tion of wider and wider fields of phenomena, analogies
from known proximate causes — which aided us in our
more specialized researches — begin to fail us; and
so our wider theoretical conceptions — about atoms,
electrons, ether, etc. — must ever remain more or
less probable hypotheses, never fully verified. When,
finally, we inquire into the absolutely ultimate origin,
nature, and destiny of the universe, where analogies
fail us altogether, we must abandon induction proper,
which seeks to compare and classify the cau.ses it dis-
covers, and have recourse to the a posteriori argument,
which simply infers, from the existence of an effect,
that there must exist a cause capable of producing it,
but gives us no further information about the nature
of this cause than that it must have higher perfection,
excellence, being, than the effect produced by it.
Such, for instance, are the arguments by which we
prove the existence of God.
IV. Historical. — Scientific induction, as just set forth, was not unknown to Aristotle and the medie\-al scholastics. It is not, however, the process referred to by Aristotle as iiraywyn (Anal. Prior., II, 2?) and usually descril)ed as the "inductive .syllogism", or "enumerative induction ". This is simply the process of inferring that what can be predicated of each member of a class separately can be predicated about the whole class. It is of no scientific value; for, w hen the enumeration of instances is perfect, or complete, the conclusion is not a scientific universal, a general law, but a mere collective universal; and when the enumeration of individuals is imperfect, or incom- plete, the collective conclusion is hazardous, more or less probable, but not certain. Aristotle was, how- ever, well aware of the possibility of reaching a certain conclusion after an incomplete enumeration of in- stances, by abandoning mere enumeration and undertaking an analysis of the nature of the instances as in modern iiuluction. He refers to this process repeatedly under the name of i/nreLpia in the "Pos- terior Analytics" (c. xix; xxxi; i, §4; cf. Rhet., II: irapdSaytui), though he did not investigate the con- ditions under which such analy.sis would produce certitude. The prevalent belief that the medieval scholastics treated only "enumerative induction" is erroneous. They were also familiar with scientific induction, using the terms experimentum, cxperienlia, to translate Aristotle's lixirtipla. Albertus Magnus (In An. Post. I, tr. I, c. ii, iii). Duns Scotus (I Sent., dist. iii, q. iv, n. 9), and St. Thomas Aquinas (In An. Post. II, lect. xx) examined it, without, however, attempting to treat of the conditions of its applica- tion, for the very good reason that the apparatus for scientific research did not exist in thei- day. But the achievements of Roger Bacon, a Fran'iiscan monk of the thirteenth century, in this directioi, are perhaps sounder than those of his better kno\'n namesake, Francis Bacon, of the sixteenth and seventeenth.
