LXVII. We shall conclude this discourse, by pointing out three capital
errors, which are derived from want of proper attention in making
experiments. The first is, that of taking for the effect, what in reality
is the cause, and taking for the cause, what is nothing more than the
effect. The second consists in taking for the cause, something that comes
in by accident, and which has no influence whatever. The third consists,
in between two effects proceeding from one and the same cause, taking one
of them for the cause of the other. I shall give examples of these three
errors, in observations appertaining to medicine, which are said to be
derived from experience, because mistakes in this branch, are generally
attended with worse consequences, than those in other ordinary physical
matters.
LXVIII. It happens, that a man feels an ardent and extraordinary thirst
upon himself, without being able to assign any apparent cause of it;
he drinks water to great excess, and in a few hours is seized with a
fever, or an acrid fluxion. It is common in such cases, to attribute
the indisposition to the excessive drinking of water, and to apprehend,
that was the cause of the disease; but this was so far from being the
case, that the indisposition was rather the cause of his drinking to that
excess. But I would have it observed, that I speak of an instance, in
which the thirst was not brought on by any manifest or apparent cause,
such as the having used any violent exercise, or having been exposed
to some great heat, either of the sun or fire, or having been a long
time without drinking, or having eaten something very salt. I say that
agreeable to this state of the case, it is very clear, that the thirst
must have arisen from some internal cause; but the question is, from what
cause? Why it could be from no other, than a morbific disposition, that
had begun to prevail within his body; or let us express it in another
manner, and say, that it proceeded from an acrid or salt humour, which
had just begun to get in motion, and by vellicating the fibres that
produce the sensation of thirst, had by that means excited it. Every
preternatural and extraordinary effect, demands a preternatural and
extraordinary cause to occasion it; and if we suppose that the thirst was
such an effect, and we cannot assign any external cause to which we can
attribute it; we must conclude that it proceeded from some preternatural
internal cause; which in all probability, must be the morbific
disposition.
LXIX. The want of this reflection, occasions great errors to be committed
in physic, for by running counter to the course of nature, you must
unavoidably mistake the road that leads to the cure. The consequence
of mistaking the effect for the cause, is administering as a medicine,
what in reality is poison; for it is clear, that if the physician
apprehends the humidity and coldness of the water to be the cause of the
distemper, when in truth it was produced by the acrid, salt, peccant, or
inflammatory humour, I say if this should happen to be the case, and he
calculates his prescriptions to correct the humidity and coldness, he by
so doing, will inflame and increase the original disorder.
LXX. This species of error, is not confined to the case we have
instanced, but is capable of being extended to a vast expanse. I am much
inclined to think, that all the extraordinary and vehement emotions, both
of the irascible, and libidinous kind, which precede distempers a small
distance of time before they make their appearance, and for which you can
assign no special external cause, are the effects of those distempers, in
their original stages; I mean, that in the first agitations of such cases
as we are speaking of, a person is apt to fall into violent passions upon
very slight provocations, such as he knows by his own experience, were
never used to agitate or have that effect on him, and either immediately,
or within a few hours afterwards, he is seized with a fever. People are
apt to suppose, that the passion was the cause of the disease; but I say,
that the disease occasioned the anger; for if this man, agreeable to his
natural disposition, was never subject to such violent starts of passion,
upon such, or even greater provocations, it necessarily follows, that
that which he experienced upon this occasion, must have been the effect
of some preternatural internal cause, which lay concealed within him,
most probably the first fermentative movements of the peccant humour,
which soon afterwards produced a fever. In reality, it is easy for any
one to perceive, and I have remarked it many times both with respect
to myself and others, that the irascible passion, is much more apt to
be inflamed upon slight occasions, in those first stages, or almost
insensible beginnings of such indispositions as tend to be somewhat
serious, than at other times.
LXXI. I do not however deny, that the ardour of passion may excite a
fever; for this without doubt, may have a great share in producing such
an effect, and we may reasonably suppose that it has, and especially in
such people as are of a choleric disposition; but when this is not the
case, we should rather suppose, that the passion tended to augment the
indisposition which followed the sudden fit of anger, and which would
have made its appearance without the intervention of that anger, although
it might have been attended with milder symptoms. And the same we say
of anger, is applicable to sadness and fear also, for they conformable
to the language of the philosophers, are passions appertaining to the
irascible.
LXXII. We may reason in the same general way, upon the effects of the
amorous passion. All vehement desires for ordinary objects, which
frequently present themselves to a man’s view, and which are totally
unusual to him, and for which we cannot assign any special external
circumstance that should excite those desires, we should conclude,
that they proceed from some preternatural internal disposition. The
indulgences or gratifications of these extraordinary desires, are always
attended with actions of excess, to which are generally attributed the
indisposition that follows them; but in truth, the indisposition which
laid concealed, irritated the appetite, and was the cause of the excess,
and not the excess of the indisposition.
LXXIII. The following mistake also, is very frequently fallen into. A
person who has always been indifferent about this or that particular
food, we will say lettuces for example, all of a sudden takes a great
fancy for them, and will eat two or three large ones. If he is afterwards
attacked with a pain of the head, and defluxion upon the breast, or a
diarrhœa, the fault is sure to be laid upon the lettuces, which are
accused as the cause of all the mischief; but in reality, the mischief
had before crept into the constitution, and had induced the extraordinary
desire to eat the lettuces.
LXXIV. I would not however, be understood to insinuate, that eating of
any thing to excess, does not frequently occasion or bring on various
diseases; for I only mean that my position should be understood to allude
to a desire that is vehement, and unusual to the person, and for which,
you can assign no visible external cause that should excite it; for under
such circumstances, there is a necessity for concluding it was owing to
some internal cause, that was sufficiently powerful to merit the name
of a morbific disposition; which is an appellation it could not have
deserved, if the appetite although extraordinary, had not been excessive.
LXXV. I am confirmed in the truth of the remark I have just made, by the
reflexion, that a diversity of appetites, must undoubtedly proceed from a
diversity or alteration of temperaments; and it follows of course, that
every alteration in the temperament, must be attended with an alteration
of the appetite. It is easy to discern, that no sick person, preserves
his appetite in the same even state, in which it continues when he is
in health; and this not only with respect to the quantity he eats and
drinks; but with respect to the quality of his nourishment also; nor is
this confined to the objects of his palate only, but extends to those of
all his other feelings and inclinations, both internal and external.