Descartes's two tests for mind (and especially for animal mind)
(From Descartes's Discourse on Method, Part V.)
Intuitive uncritical formulation of the Language Test: "The first
[of these two very certain means of recognizing that God-made humanlike
machines are not true humans] is that they could never use words or other
signs, composing them as we do in order to declare our thoughts to others.
Critical formulation of the Language Test: "For one can readily conceive that a machine might be made in such a way that it produces words, and even that it produces some words relevant to the corporeal actions that effect some change in its organs, e.g., that if one touches it in a certain place, it will ask what one wishes to say to it; and that if one touches it in another place, it will exclaim that one is hurting it, and the like. But one cannot conceive that the machine could arrange words so diversely as to respond to the meaning of all that might be said in its presence, as even the most stupid human beings can do. " AT VI, 56 (Massey's translation; translator's insertions are always in brackets).
[That is to say, the test consists in determining whether the subject
can furnish an appropriate verbal response to anything that might be said
in its presence.]
Original French text: Car on peut bien concevoir qu'une machine
soit tellement faite qu'elle profere des paroles, & mesme qu'elle en
profere quelques unes a propos des actions corporelles qui causeront quelque
changement en ses organes: comme, si on la touche en quelque endroit, qu'elle
demande ce qu'on lui veut dire; si en un autre, qu'elle crie qu'on lui
fait mal, & choses semblables; mais non pas qu'elle les arrenge diversement,
pour repondre au sens de tout ce qui se dira en sa presence, ainsi que
les hommes les plus hebetez peuvent faire. (AT VI, 56-57; diacritical marks
omitted.)
First version of the Action Test: "And the second [very certain
means of recognizing that God-made humanlike machines are not true humans]
is this. Although such machines might do a number of things as well as
or perhaps better than any of us, they would inevitably flounder ineffectually
in some others. By these ineffectual flounderings one would discover that
they do not act through understanding but solely through the disposition
of their organs. For whereas reason is a universal instrument which is
of service in all situations, these organs need a particular disposition
for each particular action. From this it follows that it is morally impossible
that there be enough diversity of organs and dispositions in a machine
to make it act in all life situations in the same way that our reason causes
us to act."
Critical version of Action Test: "It is also a very remarkable
thing that, although there are a number of animals that manifest more practical
intelligence in some of their actions than we do, one nonetheless observes
that in many other actions these same animals manifest no practical intelligence
at all, so that what they do better than us does not prove that they partake
of mind; for, on this score, they would partake more of mind than any of
us does, and so would do better at everything. It proves, rather, that
they don't partake of mind at all, but that it is Nature which acts in
them according to the disposition of their organs. Similarly, people recognize
that a clock, which is composed only of wheels and springs, can count the
hours and measure time more exactly than we can with all our practical
wisdom." (AT VI, 58-59; Massey's translation)
French text of critical version of Action Test: C'est aussi une chose fort remarquable que, bien qu'il y ait plusieurs animaux qui tesmoignent plus d'industrie [key word "industrie" can mean something like practical intelligence] que nous en quelques unes de leurs actions, on voit toutefois que les mesmes n'en tesmoignent point du tout en beaucoup d'autres: de facon que ce qu'ils font mieux que nous, ne prouve pas qu'ils ont de l'esprit; car, a ce conte, ils en avroient plus qu'aucun de nous, & feroient mieux en toute chose; mais plutost qu'ils n'en ont point, & que c'est la Nature qui agist en eux, selon las disposition de leurs organes: ainsi qu'on voit qu'un horologue, qui n'est compose que de roues; & de ressors, peut conter les heures, & mesurer le tems, plus iustement que nous avec toute nostre prudence. (AT VI, 58-59; diacritical marks omitted.)