Biology Reference
In-Depth Information
section, I use a more informal approach to develop an understanding of what it
would entail for a collection of material components to become self-fabricating.
As mentioned above, the interpretation of objects in the diagrams in terms of
Aristotelean causes is also due to Rosen.
5. HOW TO CONSTRUCT A SELF-FABRICATING FACTORY
Just as Shakespeare surely found it more profitable to compare his love to a
summer's day than to a rock or a whale, we, in order to understand the nature
and logical requirements of a self-fabricating system, need to find a useful
image to compare it with. From the long line of machine metaphors that have
since Descartes been used to describe organisms - through hydraulic automata,
clockworks, steam engines, servomechanisms and computers to the vending
machine (stick in a gene, pull out a product) - the image of a chemical factory
is most useful for the purpose. It embodies the essence of a system that not only
consists of fabricators, but, as a whole, is also a fabricator, though, in the case
of all factories thus far made by man, not of self.
Let us, therefore, begin by considering a man-made factory as an generalised
example of a fabricator. A bird's-eye view of this factory could be Fig. 3a:
the factory L is a black box that transforms raw materials P (its input) into
products Q (its output). P and Q can be single objects or collections of objects.
Fig. 3a) is also a graphical equivalent of the mappings described in Eqn. (1).
Q can of course be used as input for another 'downstream' factory M that
transforms it to R (Fig. 3b). Zooming our view out even further, L and M may
even be viewed as a single factory LM that produces R from P. However, instead
of zooming out, let us zoom into the details of our factory. Now, instead of
representing the factory as such, L could represent an agent or machine (a simple
fabricator) inside the factory; L performs the elementary task of transforming an
intermediate widget P somewhere in the production process into the next widget
Q. In fact, the production process as a whole can be visualised as a network
in which simple fabrication processes are linked as in Fig. 3b. It need not be a
linear process: there could be branches where one intermediate widget is used as
input for two different processes. Branches can converge; cyclically organised
processes can occur. The details of such a transformation network are, however,
(a)
(b)
(c)
L
L
M
LM
P
Q
P
Q
R
P
R
Figure 3
single (a), linked (b) and lumped (c) fabricators.
