Some understanding of Leibniz's  insistence that "two indiscenibles can never be found among sensible things." may be gained by realizing that Leibniz was fascinated by Leeuwenhoek's discoveries with a single lens microscope.

Some quotations from Leibniz:

1.  “I had maintained that two indiscernibles can never be found among sensible things, and that, for example, we should never find two leaves in a garden, nor two drops of water which were perfectly alike”

Leibniz, “Correspondence with Clarke”, 5, 23.  In Leibniz: Philosophical Writings edited by G.H. R. Parkinson (Toronto: Everyman’s Library, 1983), p. 224.

________________________________________________________________

2. “When I deny that there are two drops of water perfectly alike, or two other bodies indiscernible from one another, I do not mean that it is absolutely impossible to suppose them, but that it is a thing contrary to Divine wisdom and consequently that it does not exist.”

(Ibid, 5, 25, p. 225).

__________________________________________________________________

3.  “Each portion of matter may be conceived as a garden full of plants, and as a pond full of fish.  But every branch of each plant, every member of each animal, and every drop of their liquid parts is itself likewise a similar garden or pond.”

Leibniz, Monadology, 67, Ibid., p. 190.

_________________________________________________________________

4. “Our experience is in favor of this great number of living things; we find that there is a prodigious quantity of them in a drop of water tinctured with powder and with one blow millions of them can be killed so that neither the frogs of the Egyptians not the quails of the Israelites...at all approach this number...
    ...[A]s nothing is so solid that it has not a certain degree of fluidity, perhaps the block of marble itself is only a mass of an infinite number of living bodies like a lake full of fish, although such living bodies can be ordinarily distinguished by the eye only When the body is partially decayed.”

Leibniz, “Letter to Arnauld, 30 April 1687”, quoted in The Invisible World: Early Modern Philosophy and the Invention of the Microscope by Catherine Wilson (Princeton: Princeton University Press, 1995), p. 208.

_________________________________________________________________

5.     “Now nothing better corroborates the incomparable wisdom of God than the structure of the works of nature, particularly the structure which appears when we study them more closely with a microscope.  It is for this reason, as well as because of the great light which could be thrown upon bodies for the use of medicine, food, and mechanical ends, that it should be most necessary to push our knowledge further with the aid of microscopes.  There are scarcely ten men in the world who are carefully at work on this, and if there were a hundred thousand, there would not be too many to discover the important wonders of this new world which makes up the interior of ours and which is capable of making our knowledge a hundred thousand times greater than it is.  It is for this reason that I have more than once hoped that the great princes might be led to arrange for this and to induce men to work at it.  Observatories have been founded for watching the stars, whose structures are spectacular and demand great apparatus, but telescopes are far from being as useful and from revealing the beauties and varieties of knowledge which microscopes reveal.  A man in Delft  [Leeuwenhoek] has accomplished wonders at it, and if there were many others like him, our knowledge of physics would be advanced far beyond its present state.  It behooves great princes to arrange this for the public welfare, in which they are most interested.  And since this matter involves little cost and display, is very easy to direct, and needs very little but good will and attention to accomplish it, there is little reason to neglect it.  As for me I have no other motive in recommending this research than to advance our knowledge of truth and the public good, which is strongly interested in the increase of the treasure of human knowledge”

Leibniz: “Reflections on the Common Concept of Justice” (1702?) in Philosophical Papers and Letters, of Leibniz, edited by Leroy E. Loemker (Boston: D. Reidel Publishing Company,1976) p. 566.
____________________________________________________________________________

Brian J. Ford has extensively researched the single lens microscope and has recently provided images on his website of Leewenhoek's specimens sent to the Royal Society.  Explore his research on Leeuwenhoek's microscope. 
 

Back to Betsy's home page
_________________________________________________________________