This, then, is the objection to immortality; and the next thing in order for me is to try to make plain to you why I believe that it has in strict logic no deterrent power. I must show you that the fatal consequence is not coercive, as is commonly imagined; and that, even though our soul's life (as here below it is revealed to us) may be in literal strictness the function of a brain that perishes, yet it is not at all impossible, but on the contrary quite possible, that the life may still continue when the brain itself is dead.
The supposed impossibility of its continuing comes from too superficial a look at the admitted fact of functional dependence. The moment we inquire more closely into the notion of functional dependence, and ask ourselves, for example, how many kinds of functional dependence there may be, we immediately perceive that there is one kind at least that does not exclude a life hereafter at all. The fatal conclusion of the physiologist flows from his assuming offhand another kind of functional dependence, and treating it as the only imaginable kind.
When the physiologist who thinks that his science cuts off all hope of immortality pronounces the phrase, "Thought is a function of the brain," he thinks of the matter just as he thinks when he says, "Steam is a function of the teakettle," "Light is a function of the electric circuit," "Power is a function of the moving waterfall." In these latter cases the several material objects have the function of inwardly creating or engendering their effects, and their function must be called productive function. Just so, he thinks, it must be with the brain. Engendering consciousness in its interior, much as it engenders cholesterin and creatin and carbonic acid, its relation to our soul's life must also be called productive function. Of course, if such production be the function, then when the organ perishes, since the production can no longer continue, the soul must surely die. Such a conclusion as this is indeed inevitable from that particular conception of the facts.
Rut in the world of physical nature productive function of this sort is not the only kind of function with which we are familiar. We have also releasing or permissive function; and we have transmissive function.
The trigger of a crossbow has a releasing function: it removes the obstacle that holds the string, and lets the bow fly back to its natural shape. So when the hammer falls upon a detonating compound. By knocking out the inner molecular obstructions, it lets the constituent gases resume their normal bulk, and so permits the explosion to take place.
In the case of a colored glass, a prism, or a refracting lens, we have transmissive function. The energy of the light, no matter how produced, is by the glass sifted and limited in color, and by the lens or prism determined to a certain path and shape. Similarly, the keys of an organ have only a transmissive function. They open successively the various pipes and let the wind in the air chest escape in various ways. The voices of the various pipes are constituted by the columns of air trembling as they emerge. But the air is not engendered in the organ. The organ proper, as distinguished from its air chest, is only an apparatus for letting portions of It loose upon the world in these peculiarly limited shapes.
My thesis now is this: that, when we think of the law that thought is a function of the brain, we are not required to think of productive function only; we are entitled also to consider permissive or transmissive function. And this the ordinary psychophysiologist leaves out of account.[28][!--Note--]
The question of the validity of an analogy in reasoning is always, as here, whether the similarity on which the reasoning rests really runs between the two cases in hand, or is not merely a general resemblance expressed by some phrase or word which seems to mean more than it does. In other words, when you are testing an analogy, whether your own or an opponent's, make sure that the similarity is real for the present case. A picturesque figure of speech may add life to an argument, but it may also cover a gap in the reasoning.
36. Reasoning by Classification or Generalization. Obviously the strength of reasoning from analogy increases with the number of cases which you can point to as showing the similarity on which you rely, for you can then begin to generalize and classify.
Analogy expresses our natural tendency to assimilate the new to the old, to interpret what is strange and unfamiliar in the light of what we already know. It may therefore be described as classification in the making. The resemblances which guide us are called analogies so long as they are newly seen, rare, or doubtful; but as the number of cases increases, analogy passes by insensible stages into established classification.[29][!--Note--]