EXP 
the greatest master in science, Sir Isaac 
Newton, reckoned four, which are as fol- 
lows : 
1. More causes of natural things are not 
to be admitted, than are both true, and 
sufficient to explain the phaenomena; for 
nature does nothing in vain, but is simple, 
and delights not in superfluous causes of 
things. 
2. And, therefore, of natural effects of 
the same kind, the same causes are to be 
assigned, as far as it can be done ; as of 
respiration in man and beasts, of the descent 
of stones in Europe and America, of light 
in a culinary fire and in the sun, and of 
the reflection of light in the earth and in 
the planets. 
3. The qualities of natural bodies which 
cannot be increased or diminished, and 
agree to all bodies in which experiments 
can be made, are to be reckoned as the 
qualities of all bodies whatsoever : thus, 
because extension, divisibility, hardness, 
impenetrability, mobility, the vis inter- 
tiae, and gravity, are found in all bodies 
which fall under our cognizance or inspec- 
tion, we may justly conclude they belong 
to all bodies whatsoever, and are therefore 
to be esteemed the original and universal 
properties of all natural bodies. 
4. In experimental philosophy, proposi- 
tions collected from the phaenomena by in- 
duction, are to be deemed (notwithstanding 
contrary hypotheses) either exactly or very 
nearly true, till other phaenomena occur, 
by which they may be rendered either 
more accurate, or liable to exception. 
This ought to be done, lest arguments of in- 
duction should be destroyed by hypothesis. 
These four rules of philosophizing are 
premised by Sir Isaac Newton to his third 
book of the “ Principia;” and more parti- 
cularly explained by him in his “ Optics,” 
where he exhibits the method of proceeding 
in philosophy, the first part of which is as 
follows •: ' 
“As in mathematics, so in natural history, 
the investigation of difficult things, by way 
of analysis, ought always to precede the 
method of composition. This analysis con- 
sists in making experiments and observa- 
tions, and in drawing general conclusions 
from them by induction (i. e. reasoning 
from the analogy of tilings by natural con- 
sequence) and admitting no objections 
against the conclusions, but what are taken 
from experiments or certain truths. And 
although the arguing from experiments and 
EXP 
observation, by induction, be no demon- 
stration of general conclusions, yet it is the 
best way of arguing which the nature of 
things admits of, and may be looked on as 
so much the stronger, by how much the 
induction is more general; and if no excep- 
tion occur from phenomena, the conclusion 
may be pronounced generally; but if, at 
any time afterwards, any exception shall 
occur from experiments, it may then be 
pronounced with such exceptions : by this 
way of analysis we may proceed from com- 
pounds to ingredients, and from motions to 
the causes producing them ; and, in gene- 
ral, from effects to their causes ; and from 
particular causes to more general ones, till 
the argument ends in the most general : 
this is the method of analysis. And that of 
synthesis, or composition, consists in assum- 
ing causes, discovered and established as 
principles, and by them explaining the phae- 
nomena, proceeding from them, and prov- 
ing the explanations.” See Acoustics, 
Aerostation, Electricity, Hydrosta- 
tics, Magnetism, Mechanics, Optics, 
Pneumatics, &c. &c. 
EXPERIMENTUM crucis , a capital, 
leading, or decisive experiment ; thus term- 
ed, either on account of its being like a 
cross or direction post, placed in the meet- 
ing of several roads, guiding men to the 
true knowledge of the nature of that thing 
they are inquiring after ; or, on account of 
its being a kind of torture, whereby the na- 
ture of the thing is, at it were, extorted by 
force. 
EXPIRATION, in physic, that part of 
respiration whereby the air is expelled, or 
driven out of the lungs. See Physiology. 
EXPLOSION, in natural philosophy, a 
sudden and violent expansion of an aerial, 
or other elastic fluid, by which it instantly 
throws off any obstacle that happens to be 
in the way, sometimes with incredible 
force, and in such a manner as to produce 
the most astonishing effects. It differs 
from expansion in this, that the latter is a 
gradual and continued power, acting uni- 
formly for some time, whereas, the former 
is always sudden, and only of momentary 
duration. The expansions of solid bodies 
do not terminate in violent explosions, on 
account of their slowness, and the small 
space through which the metal, or pther 
expanding substance, moves. Thus wedges 
of dry wood driven into stone, and wetted, 
will cleave the most solid blocks, but they 
never throw the parts to any distance, as 
H 2 
