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"P is knowable experientially" =df "It is humanly
possible to know P either by direct appeal to experience or by
valid inference from propositions one or more of which is known
experientially".
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Comments:
- "experiential" and "a posteriori" are synonyms.
- "experiential" does not mean either "experimental" or
"empirical".
- The phrase "valid inference" is not to be taken to mean
"deductively valid inference". It is to be understand to mean
"deductively or inductively valid inference".
- Be careful not to read into this definition more than it states.
In particular, do not assume that one's knowledge must derive from one's
own experience. Indeed a very great deal of our knowledge is obtained
from other persons – persons who were present at events at which we ourselves
were not, persons who have more acute senses than the rest of us, etc.
Knowledge need not be firsthand: it can be second-, third-, or ...-hand.
- The definition (above) is recursive, as is the next. See
"Definitions,
Dictionaries, and Meanings".
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"P is knowable ratiocinatively" =df "It is humanly
possible to know P by appeal to reason (e.g. by an analysis of
concepts) or by valid inference from propositions which
themselves are known by appeal to reason."
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Comments:
- Note that the parenthetical phrase begins "e.g." The meaning
would change dramatically if it were instead "i.e."
- Mathematicians will insist that "valid" be taken to mean
"deductively valid" for the case of mathematical logic.
Problems:
The two definitions above – although certainly standard and familiar –
have some peculiar and unexpected, indeed perhaps paradoxical, consequences.
If you are interested in learning what they are, see
"Getting
from P to Q: Valid Inference and Heuristics", by Norman Swartz,
in Dialogue, vol. XXXII (1993), pp. 527-540.
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"P is knowable empirically" =df "It is humanly
possible to know P only experientially."
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"P is knowable a priori" =df "It is humanly possible
to know P other than experientially [i.e. without
experience]."
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Comment:
(Note " " stands for "implies".)
- empirical experiential (but not conversely)
- ratiocinative a priori (but not conversely)
RATIONALISM is the philosophical theory that there are at least
some contingent propositions that can be known a priori.
For example, (it is sometimes alleged that) it stands to reason
that (i.e. it may be known by
reason alone [ratiocinatively], and hence a priori, that)
- Heavier objects fall faster than light ones.
- If there are 5 persons in a room and none leave, then if 6
persons enter that room, there will be 11 persons in that room.
- If a table measures 110cm when measured left-to-right, then
it will measure 110cm when measured right-to-left.
- If a train is traveling 30km/h due east, and if a
passenger is walking in that train from the rear towards the
engine at 5km/h with respect to the train, then that person
is traveling east at 35km/h with respect to the ground.
- To get greater fuel economy in a car, one should turn off
the air-conditioning and open the windows.
- Everything that is colored is extended.
- Nothing can be in two places at the same times (or, more exactly,
nothing can have its entire spatial extent present at the same time in
two unconnected spatial locations).
- Nothing can be both red and blue all over at the same time in the
same place.
EMPIRICISM (for present purposes) is the philosophical theory
that contingent propositions are never knowable a priori, i.e.
that if a contingent proposition is knowable at all, then it is
knowable empirically, i.e. only by experience.
Empiricists will deny of all the claims immediately above, and indeed
of any and all others, that they are both contingent and knowable a
priori. Of any specific claim that a Rationalist might put forward
as a candidate for being both contingent and knowable a priori, an
empiricist will argue that:
- the claim is not contingent, but is noncontingent; or
- the claim, although contingent, is not knowable a priori; or
- the claim is not knowable (by any means – either empirically or
a priori).
Twentieth- and twenty-first-century empiricism needs to be distinguished from eighteenth-century,
or, as it is often called, British Empiricism. Eighteenth-century empiricism
claimed two things:
- (The equivalent of) what has been said of Empiricism above; and
- All our concepts are derived through sensory experience. There are
no innate concepts.
The former of these two theses is (now known as) Judgment Empiricism; the
latter, Concept Empiricism. All twentieth-century empiricists are judgment
empiricists; some, but not all (perhaps even not many) are concept empiricists.
If you find that an author cursorily dismisses 'Empiricism' (or 'British
Empiricism'), he/she is likely railing against Concept Empiricism. But
you'll have to examine the context of the argument to be sure.
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Notes
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