The English works of Thomas Hobbes of Malmesbury, Volume 07 (of 11)
Thomas Hobbes · en
That is, if there be propounded a row of quantities in duplicate
proportion of arithmetically-proportionals (or according to the row of
square numbers) continually increasing, and beginning with a point or O.
The proportion of that row to a row of so many equals to the greatest,
shall be greater than subtriple proportion, and the excess shall be that
proportion which unity hath to the sextuple of the number of terms after
0, or the same which the square root of the first number after 0, hath
to the sextuple of the square root of the greatest.
For proof whereof you have no more here than _patet ex præcedentibus_;
and no more before but _adeoque_. You do not well to pass over such
curious propositions so slightly; none of the ancients did so, nor, that
I remember, any man before yourself. The proposition is false, as you
shall presently see.
Take, for example, any one of your rows: as (0 + 1 + 4)/(4 + 4 + 4). By
this proportion of yours 1 + 4, which makes 5, is to 12 in more than
subtriple proportion; by the proportion of 1 to the sextuple of 2 which
is 12. Put in order these three quantities 5, 4, 12, and you must see
the proportion of 5 to 12 is greater than the proportion of 4 to 12,
that is, subtriple proportion, by the proportion of 5 to 4. But by your
account the proportion of 5 to 4 is greater than that of 4 to 12 by the
proportion of 1 to 12. Therefore, as 5 to 4 so is 1 to 12, which is a
very strange paradox.
After this you bring in this consectary: “_Cum autem crescente numero
terminorum excessus ille supra rationem subtriplam continue minuatur, ut
tandem quovis assignabili minor evadat (ut patet) si in infinitum
producatur, prorsus evaniturus est. Adeoque._”
That is, seeing as the number of terms increaseth, that excess above
subtriple proportion continually decreaseth, so as at length it becomes
less than any assignable (as is manifest) if it be produced infinitely,
it shall utterly vanish, and so. And so what?
Sir, this consequence of yours is false. For two quantities being given,
and the excess of the greater above the less, that excess may
continually be decreased, and yet never quite vanish. Suppose any two
unequal quantities differing by more than an unit, as 3 and 6, the
excess 3, let 3 be diminished, first by an unit, and the excess will be
2, and the quantities will be 3 and 5; 5 is greater than 4, the excess
1. Again, let 1 be diminished and made (1)/(2), the excess 4 and the
quantities 3 and 4(1)/(2), 4(1)/(2) is yet greater than 4. Again
diminish the excess to (1)/(4), the quantities will be 3 and 4(1)/(4),
yet still 4(1)/(4) is greater than 4. In the same manner you may proceed
to (1)/(8) (1)/(16) (1)/(32), &c. infinitely; and yet you shall never
come within an unit (though your unit stand for 100 miles) of the lesser
quantity propounded 3, if that 3 stands for 300 miles. The excesses
above subtriple proportion do not decrease in the manner you say it
does, but in the manner which I now shall show you.