Lotze's Local Signs

by Corry Shores
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In Time and Free Will, (Essai sur les données immédiates de la conscience), Bergson claims that Lotze's theory of local signs treats sensations as inextensive. Hence it resembles Kant's theory of our a priori intuition of space. (Bergson 93)

In a manner reminiscent of Kant's a priori, Lotze writes in his Metaphysic:

spatiality is only our form of apprehension, perhaps also a form belonging to every being that has a mind. (Lotze 481d)

And this form of apprehension we may reduce to the structure of our own bodies. (481d)

But, Lotze also presumes that the world around us is extended in space (482a). Bergson's observation, however, is

1) that Lotze is really only concerned with showing how our sense of spatiality is a product of our sensations themselves,

2) that these sensations are "unextended and simply qualitative: extensity is supposed to result from their synthesis, as water from the combination of two gases" (Bergson 93c), and

3) that Lotze, like Kant, makes a radical distinction between the "matter of representation and its form" (93bc).

In the Metaphysic, Lotze notes that spatial relations

come to our knowledge not by the mere fact of their existence, but only through a co-ordination of their effects upon us, a co-ordination which corresponds to the relative position of the points from which those effects proceeded. (482c)

Lotze takes our nerve fibres to be our means of sensation. The question is, how do our nerves come to sense the spatiality of the world around us? For,

all those geometrical relations which exist among the sense-stimuli and among the nervous excitations they occasion must completely disappear in the moment when they pass over into the soul: for in its point of unity there is no room for their expansion. Up to this point the single impressions may be conducted by isolated nerve-fibres which preserve the special nature of each impression; even in the central portions of the nervous system similar separations may still exist, although we do not know that they do so; but in the end, at the transition to consciousness, all walls of partition must disappear. In the unity of consciousness these spatial divisions no more exist than the rays of light which fall from various points on a converging lens continue to exist side by side in the focal points at which they intersect. (484-485)

...

This perception cannot be delivered to us ready-made. The single impressions exist together in the soul in a completely nonspatial way and are distinguished simply by their qualitative content, just as the simultaneous notes of a chord are heard apart from one another, and yet not side by side with one another, in space. From this non-spatial material the soul has to re-create entirely afresh the spatial image that has disappeared; and in order to do this it must be able to assign to each single impression the position it is to take up in this image relatively to the rest and side by side with them. (485b)

Our mind needs some indicator to tell it how to arrange the despatialized impressions into a spatialized form.

some clue will be needed, by the help of which it may find for each impression the place it must take, in order that the image that is to arise in idea may be like the spatial figure that has disappeared. (485c)

To illustrate what this "clue" might be like, Lotze describes how we disassemble and reassemble products by means of numerical coding:

Let us suppose that a collection has to be arranged in some new place in exactly the same order that it has at present. There is no need to keep this order intact during the transport ; we do whatever is most convenient for the purposes of transport, and when it is finished we arrange the several pieces of the collection by following the numbers pasted on them. Just such a token of its former spatial position must be possessed by each impression, and retained throughout the time when that impression, together with all the rest, was present in a non-spatial way in the unity of the soul. (485d)

But, he explains, the stimuli coming from the different points of the spatial object hit different points of our sense organs.

Where then does this token come from? It cannot be the point in external space from which the sense-stimulus starts, that gives to it this witness of its origin. A blue ray of light may come from above or from below, from the right or from the left, but it tells us nothing of all this; it itself is the same in all cases. It is not until these similar stimuli come in contact with our bodies that they are distinguished, and then they are distinguished according to the different points at which they meet the extended surface of our organs of sense. This accordingly may be the spot at which the token I am describing has its origin, a token which is given along with the stimulus in consequence of the effects produced by it at this spot, and which in the case of each single stimulus is distinct and different from that given along with any other stimulus. (485-486)

So in other words, each nerve has a different place on our sense organs. The spatialized object has different points spatially relative to each other. To each one of our sense-organ-points corresponds an impression of each one of the spatial-object's points. Then, extra "information" is "coded" with each fiber, like the numerals of the disassembled product. Then, our mind "reassembles" the sense impressions so that the spatial dimensions of the image are proportional to those of the sensed object. [Here we see a sort of sensation isomorphism.]

Each single fibre, at the spot where it receives the stimulus, can attach to it the extra-impression described, and can transmit it to consciousness, stamped with this character, and preserved by the isolation of the fibre from mixture with other physical excitations. (486d)

Thus we must assume that there is a physiological way that each nerve signal is inscribed in this way.

We must suppose that similar stimuli give rise in each nerve-fibre to a special extra-impression, an extra-impression which is different in the case of every single fibre, and which connects itself, in the manner of an association, with that main impression which depends on the quality of the stimulus,—connects itself, therefore, in such a way that neither of the two impressions, the main one and the extra one, interferes with the peculiar nature and tone of the other. (486-487)

Now Lotze has us imagine how this process works. There are three categories of things we need to keep in mind.

1) the stimuli.

There are three different diverse stimuli: we call them A, B, C.

2) the sites of stimulus-reception on the sense organ:

There are three different spots on the sense organ corresponding to the three stimuli: we call them p, q, r.

3) the local signs (the extra-impressions that serve as tokens).

Each of the three sense-organ-points produces its own unique extra-impression that serves as a token for the reconfiguration of the stimuli's spatial relations: we call them p, k, r

the difference between these connected local signs p, k, r will be the clue by means of which the sensations falling upon p, q, r can be localised in separate places in our perception of space. (487d)

When we sense the object, each of the different constituent sensations will be similar. However, they will be different according to their local sign. So each similar sensation is associated with its local sign. We call each similar sensation: Ap, Ak, Ar. Each one corresponds to the sensation falling on spots p, q, r. It is on account of their different local signs that all three constituent sensations are not identical. If they were identical, the mind would fuse them into one same sensation A. But since they are different, they maintain their individuality. (488a) So, because Ap, Ak, Ar are all qualitatively different, they will not become totally fused.

Now, one same spot will receive a sequence of impressions over a span of time. That sequence for one spot we call: Ak, Bk, Ck.

The way that our minds will then sense extensive dimensions of the object is by means of a sort of arithmetic or computation. So even though the local signs are qualitatively different, they must also be quantitatively comparable. In other words, our minds receive these signals or codes, and must decode them. (491a.b) [So for example, we see a table. The left end produces Ap, the middle Ak, and the right end Ar, But the mind does not receive them in this order. In needs to know that p + k, and k + r, together equal p - r.]

So in this way, Lotze shows how the spatiality of extensive objects is stripped from them, and then reconfigured in the mind in an apriori-like way.

Images from the original text [click on the image to enlarge it]:

[Directory of other entries in this series.]

Lotze, Hermann. Metaphysic in Three Books: Ontology, Cosmology, and Psychology. Transl. of Book III, A.C. Bradley. Ed. Bernard Bosanquet. Oxford: Clarendon Press, 1884.

Available online at:

http://www.archive.org/details/metaphysicinthre00lotzrich

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:

http://www.archive.org/details/timeandfreewill00pogsgoog