In the years 1715 and 1716 a
philosophically significant correspondence occurred between Leibniz
and Samuel Clarke, a proponent of Isaac Newton. Particularly Leibniz
attacked the Newtonian idea of an absolute space and an absolute time
that exist independently of any things within them. Leibniz based his
criticism on the principle of sufficient reason: if there would be an
absolute space, God might have created world few meters away from its
actual place in the absolute space, but since all the places in an
absolute space are completely similar, He would have had no reason to
create it in any particular place and would thus have been unable to
create the world anywhere.
Instead of an absolute space and time,
Leibniz suggested a relational view of them: space and time are
nothing but orders of things – space an order of coexistent things
and time an order of successive things. An important consequence of
this view is that it becomes meaningless to speak of space and time
without any things. (Note that this view is not relativistic: spatial
and temporal magnitudes are still stable, despite the differences in
the velocity or the effects of gravity.)
Leibniz's view was accepted by Wolff,
and indeed, it appears to have been in favour throughout the German
idealism. Kant, for instance, appears to take Leibniz's view more
seriously than Newtonian absolute space: Kant attacks in Critique of
pure reason the relational view more vigorously and also appears to
apply a modified relational theory of space in his metaphysical
foundations of natural science. Indeed, presupposing an absolute space and time adds to an ontological system two rather strange entities, which are not things as such, but also not based on things.
Now, if one would take Leibniz's
description of relational view literally, one could instantly derive
all sorts of absurdities. For instance, if space was nothing more than
an order of things, space would change at once, when the order of
things changes: space would become larger, if a thing went farther
from all other things than any thing before. As Leibniz himself
appears to have been aware, these problems could be avoided by
defining space and time through possible, rather than actual order of things. Thus,
space could continue beyond the actual positions of things, because
the things have the capacity to or at least could be conceived to move
further than they are.
Wolff, on the other hand, seems not to
be aware of the possible problems and suggests that space and time
could be defined as the actual order of things. Thus, he is able to
say that even a single thing by itself would be non-spatial or that
spatiality required at least two things and their actual relation.
Because Wolff's simple things should
have no things as their constituents, their internal constitution
could not be spatial, because it would involve no actual relation of
several objects. As we noticed in the previous text, Wolffian notion
of a simple thing is ambiguous, because it leaves out the possibility
of Aristotle's potentially divisible and still actually unified
substances. Similar problems arise with Wolff's notion of space.
According to Wolff's definition, the Aristotelian divisible substance
without any actual parts would be non-spatial, which is clearly
absurd, when we think of e.g. a portion of water. Here we should
obviously add some modalities to Wolffian account of space:
Aristotelian substance is spatial, because it can be divided into
parts that have spatial relations.
Even this correction might not be
sufficient. Democritean atoms were supposedly indivisible substances,
but still spatial. Wolff notes – consistently with his own
definition of space – that this atomist notion is contradictory.
Yet, it seems quite possible to imagine that a thing would be
physically indivisible and still have some spatial magnitude:
spatiality is here not connected to a capacity to divide a thing, but
to a possibility of conceiving the division of a thing.
For Wolff, spatiality is something
connected with the inner consitution of complex things. What sort of
characteristics are then left for simple things? I shall return to
this question in the next blog text.
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