31 Dec 2008

Bergson, Time and Free Will, Chapter 1, §37 "In Photometric Experiments the Physicist Compares, not Sensations, but Physical Effects"

by Corry Shores
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[The following is summary; my commentary is in brackets.]

Bergson, Time and Free Will

(Essai sur les données immédiates de la conscience)

Chapter I, "The Intensity of Psychic States"

Part XIII: "Sensation of Light"

§37 "In Photometric Experiments the Physicist Compares, not Sensations, but Physical Effects"

Previously we considered an experiment where we placed for lit candles in front of a sheet of paper. Then we blew out the candles one by one, causing the paper to darken in successive stages. Our inclination might be to say that our sensation of the paper underwent a quantitative decrease in intensity; that is to say, we might be inclined to think that we had the same sensation of the lit paper, but that our sensation decreases as the candles were extinguished. But Bergson argues that there is not a quantitative difference between the sensations. Perceiving the black on the paper was no less intense than perceiving the light. It was merely different. So intensity for Bergson is a matter of qualitative (and not quantitative) differences of sensation.

With this in mind, Bergson will now reinterpret "photometric experiments." We consider, for example, a candle placed so far from a sheet of paper, and note how the paper is illuminated in that instance. We then move the candle double the distance away, but find that we need to add three more candles to obtain the same sensation we had with one candle at half the distance. (55a)

Here the scientist might conclude that one candle at double the length has one-fourth the luminous intensity. But we see clearly in this case that we are dealing with physical effects and not psychological effects. (55b)

For it cannot be said that you have compared two sensations with one another: you have made use of a single sensation in order to compare two different luminous sources with each other, the second four times as strong as the first but twice as far off.


So here the physicist did not compare different sensations, so he cannot speak of differences of intensity between different sensations.

The sensation of light here plays the part of the auxiliary unknown quantity which the mathematician introduces into his calculations, and which is not intended to appear in the final result.


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Images from the pages summarized above, in the English Translation [click on the image for an enlargement]:

Images from the pages summarized above, in the original French [click on the image for an enlargement]:

Bergson, Henri. Time and Free Will: An Essay on the Immediate Data of Consciousness, Transl. F. L. Pogson, (New York: Dover Publications, Inc., 2001).

Available online at:


French text from:

Bergson, Henri. Essai sur les données immédiates de la conscience. Originally published Paris: Les Presses universitaires de France, 1888.


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