1 Jan 2009

Bergson, Time and Free Will, Chapter 1, §43 "Can Two Sensations Be Equal Without Being Identical?"

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 XIV: "Psychophysics"

§43 "Can Two Sensations Be Equal Without Being Identical?"

Fechner realized that if he wanted to measure psychological states and place their values in a homogeneous quantitative scale, then he would have to define what it would mean for two psychological states to be quantitatively equal, and what it would mean to add the quantity of one simple state to another. But in the first place, he must show how they can be identical, before he can explain how we add sensations together. (63a.b)

[We might consider an object, an apple for example. We can say that it has qualitative features and extensive features. We see that it extends so far this way and that, and we see that it is red. We can then take another apple, twice as large, and green. But we can put aside the fact that their colors tell us that they are different objects, and then compare them in terms of their extensive values. Then we can say that the green apple is twice the value of the red one. But it is not twice as much of a red apple, just twice its extension. Also, we can consider psychic phenomena in this way. We can say that in one case, I am having a sensation of heat, and it is so strong. In another case I have a sensation of luminosity, and it is twice as strong. Then, we can forget that qualitatively one is a sensation of heat and the other of light, and say that the second one is twice the quantity of the first one. But we are not saying that the sensation of light is twice as much of a sensation of heat, but rather just that it is twice as much of a sensation. For this reason, Bergson says that] every phenomena and every object is presented under two aspects:

1) its qualitative aspect, and

2) its extensive aspect.

And, there is nothing to stop us from ignoring the qualitative aspects, which leaves us to focus on the extensive quantitative terms. These terms, as purely numerical, can be superposed upon each other for comparison, and thereby be deemed identical or not. (63bc)

A psychophysicist can ignore the fact that one sensation is a feeling of heat, and another one is a sensation of light. Then he may say that one is quantitatively identical to the other. But in the process, the psychophysicist

1) set out to measure the sensation of a certain determinate quality, such as of heat, and

2) completely placed out-of-the-picture its qualitative feature for the sake of measurement.

So in other words, the psychophysicist is not telling us anything about the sensation, because it has become just a numerical abstraction. But sensations we know have a quality to them.

Suppose for example we want to measure the quality of heat-sensation, and we do so by correlating it with some physical quantity, in this case, temperature gradient. Here, we are measuring quality Q by some physical quantity Q' lying beneath it. But we might consider two things:

1) Sometimes when it is cold, we are all too aware of the temperature, and so we are more sensitive to its changes, even if they are small. But other times something else has our attention, and even though we might be in the same degree of cold, and undergo the same increase in temperature, we might not be sensitive to it. So in other words, there might not be any consistent relation between the qualitative nature of our sensation and the physical quantity causing it. Which is to say, Q might not be a function of Q'.

2) It could be that even if there was a consistent correspondence between Q and Q', in order to quantify Q so to place it into correspondences with the quantified Q', we need to obtain a standard unit for Q. In order to do this, we need to compare some quantity of Q with a fraction of it, to show that it is a homogeneous quantity that we may use as a standard of measure. But our only way of determining Q is by correlating it with Q'. So we cannot establish the numerical correspondence between Q and Q', because that requires that we already know what that correspondence is. For, our only means of quantifying Q is through Q'; but, we need to already know the quantitative values of Q before we can correlate them with Q'. Thus, we cannot even begin to determine the correlation.

So psychophysicists try to measure the sensation of heat by comparing it with a degree of temperature. But, the degree of temperature is a standardized convention. What psychophysicists really want is to know is how the sensation of heat varies when you change the temperature. In other words, they want to mathematically determine the functional relation between extensive changes and intensive changes.

Consider that when we have a temperature-change sensation, even though we might think it is more or less, it presumably is never more than a sensation of heat. We do not perceive numerical values; we feel heat. But, psychophysicists want to ignore the qualitative aspect, and just look at the quantitative side of our heat sensations. However, Bergson argues that we do not have sensations of numbers or quantities. We just have sensations, which are qualitative in nature.

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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.

Available online at:




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