Medieval Sourcebook:
Roger Bacon:
On Experimental Science, 1268
Having laid down the main points of the wisdom of the Latins as
regards language, mathematics and optics, I wish now to review
the principles of wisdom from the point of view of experimental
science, because without experiment it is impossible to know anything
thoroughly.
There are two ways of acquiring knowledge, one through reason,
the other by experiment. Argument reaches a conclusion and compels
us to admit it, but it neither makes us certain nor so annihilates
doubt that the mind rests calm in the intuition of truth, unless
it finds this certitude by way of experience. Thus many have arguments
toward attainable facts, but because they have not experienced
them, they overlook them and neither avoid a harmful nor follow
a beneficial course. Even if a man that has never seen fire, proves
by good reasoning that fire burns, and devours and destroys things,
nevertheless the mind of one hearing his arguments would never
be convinced, nor would he avoid fire until he puts his hand or
some combustible thing into it in order to prove by experiment
what the argument taught. But after the fact of combustion is
experienced, the mind is satisfied and lies calm in the certainty
of truth. Hence argument is not enough, but experience is.
This is evident even in mathematics, where demonstration is the
surest. The mind of a man that receives that clearest of demonstrations
concerning the equilateral triangle without experiment will never
stick to the conclusion nor act upon it till confirmed by experiment
by means of the intersection of two circles from either section
of which two lines are drawn to the ends of a given line. Then
one receives the conclusion without doubt. What Aristotle says
of the demonstration by the syllogism being able to give knowledge,
can be understood if it is accompanied by experience, but not
of the bare demonstration. What he says in the first book of the
Metaphysics, that those knowing the reason and cause are wiser
than the experienced, he speaks concerning the experienced who
know the bare fact only without the cause. But I speak here of
the experienced that know the reason and cause through their experience.
And such are perfect in their knowledge, as Aristotle wishes to
be in the sixth book of the Ethics, whose simple statements are
to be believed as if they carried demonstration, as he says in
that very place.
Whoever wishes without proof to revel in the truths of things
need only know how to neglect experience. This is evident from
examples. Authors write many things and the people cling to them
through arguments which they make without experiment, that are
utterly false. It is commonly believed among all classes that
one can break adamant only with the blood of a goat, and philosophers
and theologians strengthen this myth. But it is not yet proved
by adamant being broken by blood of this kind, as much as it is
argued to this conclusion. And yet, even without the blood it
can be broken with ease. I have seen this with my eyes; and this
must needs be because gems cannot be cut out save by the breaking
of the stone. Similarly it is commonly believed that the secretions
of the beaver that the doctors use are the testicles of the male,
but this is not so, as the beaver has this secretion beneath its
breast and even the male as well as the female produces a secretion
of this kind. In addition also to this secretion the male has
its testicles in the natural place and thus again it is a horrible
lie that, since hunters chase the beaver for this secretion, the
beaver knowing what they are after, tears out his testicles with
his teeth and throws them away. Again it is popularly said that
cold water in a vase freezes more quickly than hot; and the argument
for this is that contrary is excited by the contrary, like enemies
running together. They even impute this to Aristotle in the second
book of Meteorology, but he certainly did not say this, but says
something like it by which they have been deceived, that if both
cold and hot water are poured into a cold place as on ice, the
cold freezes quicker (which is true), but if they are placed in
two vases, the hot will freeze quicker. It is necessary, then,
to prove everything by experience.
Experience is of two kinds. One is through the external senses:
such are the experiments that are made upon the heaven through
instruments in regard to facts there, and the facts on earth that
we prove in various ways to be certain in our own sight. And facts
that are not true in places where we are, we know through other
wise men that have experienced them. Thus Aristotle with the authority
of Alexander, sent 2,000 men throughout various parts of the earth
in order to learn at first hand everything on the surface of the
world, as Pliny says in his Natural History. And this experience
is human and philosophical just as far as a man is able to make
use of the beneficent grace given to him, but such experience
is not enough for man, because it does not give full certainty
as regards corporeal things because of their complexity and touches
the spiritual not at all. Hence man's intellect must be aided
in another way, and thus the patriarchs and prophets who first
gave science to the world secured inner light and did not rest
entirely on the senses. So also many of the faithful since Christ.
For grace makes many things clear to the faithful, and there is
divine inspiration not alone concerning spiritual but even about
corporeal things. In accordance with which Ptolemy says in the
Centilogium that there is a double way of coming to the knowledge
of things, one through the experiments of science, the other through
divine inspiration, which latter is far the better as he says.
Of this inner experience there are seven degrees, one through
spiritual illumination in regard to scientific things. The second
grade consists of virtue, for evil is ignorance as Aristotle says
in the second book of the Ethics. And Algazel says in the logic
that the mind is disturbed by faults, just as a rusty mirror in
which the images of things cannot be clearly seen, but the mind
is prepared by virtue like a well polished mirror in which the
images of things show clearly. On account of this, true philosophers
have accomplished more in ethics in proportion to the soundness
of their virtue, denying to one another that they can discover
the cause of things unless they have minds free from faults. Augustine
relates this fact concerning Socrates in Book VIII, chapter III,
of the City of God: to the same purpose Scripture says, to an
evil mind, etc., for it is impossible that the mind should lie
calm in the sunlight of truth while it is spotted with evil, but
like a parrot or magpie it will repeat words foreign to it which
it has learned through long practice. And this is our experience,
because a known truth draws men into its light for love of it,
but the proof of this love is the sight of the result. And indeed
he that is busy against truth must necessarily ignore this, that
it is permitted him to know how to fashion many high sounding
words and to write sentences not his own, just as the brute that
imitates the human voice or an ape that attempts to carry out
the works of men, although he does not understand their purpose.
Virtue, then, clears the mind so that one can better understand
not only ethical, but even scientific things. I have carefully
proved this in the case of many pure youths who, on account of
their innocent minds, have gone further in knowledge than I dare
to say, because they have had correct teaching in religious doctrine,
to which class the bearer of this treatise belongs, to whose knowledge
of principles but few of the Latins rise. Since he is so young
(about twenty years old) and poor besides, not able to have masters
nor the length of any one year to learn all the great things he
knows, and since he neither has great genius or a wonderful memory,
there can be no other cause, save the grace of God, which, on
account of the clearness of his mind, has granted to him these
things which it has refused to almost all students, for a pure
man, he has received pure things from me. Nor have I been able
to find in him any kind of a mortal fault, although I have searched
diligently, and he has a mind so clear and far seeing that he
receives less from instruction than can be supposed. And I have
tried to lend my aid to the purpose that these two youths may
be useful implements for the Church of God, inasmuch as they have
with the Grace of God examined the whole learning of the Latins.
The third degree of spiritual experience is the gift of the Holy
Spirit, which Isaiah describes. The fourth lies in the beatitudes
which our Lord enumerates in the Gospels. The fifth is the spiritual
sensibility. The sixth is in such fruits as the peace of God,
which passes all understanding. The seventh lies in states of
rapture and in the methods of those also, various ones of whom
receive it in various ways, that they may see many things which
it is not permitted to speak of to man. And whoever is thoroughly
practiced in these experiences or in many of them, is able to
assure himself and others, not only concerning spiritual things,
but all human knowledge. And indeed, since all speculative thought
proceeds through arguments which either proceed through a proposition
by authority or through other propositions of argument, in accordance
with this which I am now investigating, there is a science that
is necessary to us, which is called experimental. I wish to explain
this, not only as useful to philosophy, but to the knowledge of
God and the understanding of the whole world: as in a former book
I followed language and science to their end, which is the Divine
wisdom by which all things are ordered.
And because this experimental science is a study entirely unknown
by the common people, I cannot convince them of its utility, unless
its virtue and characteristics are shown. This alone enables us
to find out surely what can be done through nature, what through
the application of art, what through fraud, what is the purport
and what is mere dream in chance, conjuration, invocations, imprecations,
magical sacrifices and what there is in them; so that all falsity
may be lifted and the truths we alone of the art retained. This
alone teaches us to examine all the insane ideas of the magicians
in order not to confirm but to avoid them, just as logic criticizes
the art of sophistry. This science has three great purposes in
regard to the other sciences: the first is that one may criticize
by experiment the noble conclusions of all the other sciences,
for the other sciences know that their principles come from experiment,
but the conclusions through arguments drawn from the principles
discovered, if they care to have the result of their conclusions
precise and complete. It is necessary that they have this through
the aid of this noble science. It is true that mathematics reaches
conclusions in accordance with universal experience about figures
and numbers, which indeed apply to all sciences and to this experience,
because no science can be known without mathematics. If we would
attain to experiments precise, complete and made certain in accordance
with the proper method, it is necessary to undertake an examination
of the science itself, which is called experimental on our authority.
I find an example in the rainbow and in like phenomena, of which
nature are the circles about the sun and stars, also the halo
beginning from the side of the sun or of a star which seems to
be visible in straight lines and is called by Aristotle in the
third book of the Meteorology a perpendicular, but by Seneca a
halo, and is also called a circular corona, which have many of
the colors of the rainbow. Now the natural philosopher discusses
these things, and in regard to perspective has many facts to add
which are concerned with the operation of seeing which is pertinent
in this place. But neither Aristotle or Avicenna have given us
knowledge of these things in their books upon Nature, nor Seneca,
who wrote a special book concerning them. But experimental science
analyzes such things.
The experimenter considers whether among visible things, he can
find colors formed and arranged as given in the rainbow. He finds
that there are hexagonal crystals from Ireland or India which
are called rainbow-hued in Solinus Concerning the Wonders of the
World and he holds these in a ray of sunlight falling through
the window, and finds all the colors of the rainbow, arranged
as in it in the shaded part next the ray. Moreover, the same experimenter
places himself in a somewhat shady place and puts the stone up
to his eye when it is almost closed, and beholds the colors of
the rainbow clearly arranged, as in the bow. And because many
persons making use of these stones think that it is on account
of some special property of the stones and because of their hexagonal
shape the investigator proceeds further and finds this in a crystal,
properly shaped, and in other transparent stones. And not only
are these Irish crystals in white, but also black, so that the
phenomenon occurs in smoky crystal and also in all stones of similar
transparency. Moreover, in stones not shaped hexagonally, provided
the surfaces are rough, the same as those of the Irish crystals,
not entirely smooth and yet not rougher than those---the surfaces
have the same quality as nature has given the Irish crystals,
for the difference of roughness makes the difference of color.
He watches, also, rowers and in the drops falling from the raised
oars he finds the same colors, whenever the rays of the sun penetrate
the drops.
The case is the same with water falling from the paddles of a
water-wheel. And when the investigator looks in a summer morning
at the drops of dew clinging to the grass in the field or plane,
he sees the same colors. And, likewise, when it rains, if he stands
in a shady place and the sun's rays beyond him shine through the
falling drops, then in some rather dark place the same colors
appear, and they can often be seen at night about a candle. In
the summer time, as soon as he rises from sleep while his eyes
are not yet fully opened, if he suddenly looks at a window through
which the light of the sun is streaming, he will see the colors.
Again, sitting outside of the sunlight, if he holds his head covering
beyond his eyes, or, likewise, if he closes his eyes, the same
thing happens in the shade at the edges, and it also takes place
through a glass vase filled with water, sitting in the sunlight.
Similarly, if any one holding water in his mouth suddenly sprinkles
the water in jets and stands at the side of them; or if through
a lamp of oil hanging in the air the rays shine in the proper
way, or the light shines upon the surface of the oil, the colors
again appear. Thus, in an infinite number of ways, natural as
well as artificial, colors of this kind are to be seen, if only
the diligent investigator knows how to find them.
Experimental science is also that which alone, as the mistress
of the speculative sciences, can discover magnificent truths in
the fields of the other sciences, to which these other sciences
can in no way attain. And these truths are not of the nature of
former truths, but they may be even outside of them, in the fields
of things where there are neither as yet conclusions or principles,
and good examples may be given of this, but in everything which
follows it is not necessary for the inexperienced to seek a reason
in order to understand at the beginning, but rather he will never
have a reason before he has tried the experiment. Whence in the
first place there should be credulity until experiment follows,
in order that the reason may be found. If one who has never seen
that a magnet draws iron nor heard from others that it attracts,
seeks the reason before experimenting, he will never find it.
Indeed, in the first place, he ought to believe those who have
experimented or who have it from investigators, nor ought he to
doubt the truth of it because he himself is ignorant of it and
because he has no reason for it.
The third value of this science is this---it is on account of
the prerogatives through which it looks, not only to the other
sciences, but by its own power investigates the secrets of nature,
and this takes place in two ways---in the knowledge of future
and present events, and in those wonderful works by which it surpasses
astronomy commonly so-called in the power of its conclusions.
For Ptolemy in the introduction of the Almagest, says that there
is another and surer way than the ordinary astronomy; that is,
the experimental method which follows after the course of nature,
to which many faithful philosophers, such as Aristotle and a vast
crowd of the authors of predictions from the stars, are favorable,
as he himself says, and we ourselves know through our own experience,
which cannot be denied. This wisdom has been found as a natural
remedy for human ignorance or imprudence; for it is difficult
to have astronomical implements sufficiently exact and more difficult
to have tables absolutely verified, especially when the motion
of the planets is involved in them. The use of these tables is
difficult, but the use of the instruments more so.
This science has found definitions and ways through which it quickly
comes to the answer of a whole question, as far as the nature
of a single science can do so, and through which it shows us the
outlines of the virtues of the skies and the influence of the
sky upon this earth, without the difficulty of astronomy. This
part so-called has four principal laws as the secret of the science,
and some bear witness that a use of this science, which illustrates
its nature, is in the change of a region in order that the customs
of the people may be changed. In connection with which Aristotle,
the most learned of philosophers, when Alexander asked of him
concerning some tribes that he had found, whether he should kill
them on account of their barbarity or let them live, responded
in the Book of Secrets if you can change their air let them live;
if not, kill them. He wished that their air could be altered usefully,
so that the complexion of their bodies could be changed, and finally
the mind aroused through the complexion should absorb good customs
from the liberty of their environment; this is one use of this
science.
Source:
From: Oliver J. Thatcher, ed., The Library of Original Sources (Milwaukee: University Research Extension Co., 1901), Vol. V:
The Early Medieval World, pp. 369-376.
Scanned by Jerome S. Arkenberg, Dept. of History, Cal. State Fullerton
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