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Society of Mind

22.5 inference

Linking structures together into chains is one of our most useful kinds of reasoning. Suppose you learned that John gave the kite to Mary and then Mary gave the kite to Jack. You could then conclude that the kite went from John to Jack. How do we draw such conclusions? Some people think we use logic for this. A simpler theory is that we do it by fitting together Trans-frames into chains. Suppose you see two frames like these:

All A's are B' s and All B 's are C's.

Then just combine the first Origin with the second Destination to make this new deduction-frame:

All A's are C's.

To do this sort of reasoning, we have to use our isonomes to rearrange our short-term memories. But this requires more than simple chaining. For example, all older children can infer that Tweety can fly from Tweety is a bird and All birds can fly. To do this, though, one has to deal with a disparity: the first B is a bird while the second B is all birds. To be able to make such chains would be virtually useless if we could do it only when both pronome assignments were absolutely identical. Over the years, children improve their abilities to decide when two different structures are similar enough to justify making chain-links. This often requires us to recall and apply other types of knowledge at appropriate level-bands of detail.

Children take many years to learn effective ways to use their pronomes and isonomes. The youngest ones can neither rearrange their representations of physical scenes nor make the kinds of inference we're discussing here. To think like adults, we must develop and learn to use memory-controlling processes that manipulate several sets of pronome values at the same time. Just such a process was concealed in our simple script for Put the apple in the pail — which first appears to be merely a matter of assigning apple to the Origin and pail to the Destination. But you can't Put something until you Get it, so this must actually involve two Trans-frame operations. The first is for moving your hand to the apple, and the second is for moving the apple to the pail. During the transition, your pronomes have to change their roles since the apple's location is the Destination of the first Trans, but then becomes the Origin of the second Trans. No matter that this seems too obvious to state; some mental process has to switch that pronome's role.

By learning to manipulate our isonomes, we become able to combine mental representations into structures that resemble bridges, chains, and towers. Our language-agencies learn to express these in the form of compound sentences, by using conjunctive grammar words like and, because, or or. But language is not the only realm in which we learn to conceptualize — that is, to treat our mental processes almost as though they were object-things. After you solve a hard problem, you may find yourself representing the steps you took as if they were the parts of a physical structure. Doing this can enable you to reassemble them into other forms that achieve the same results with much more speed and much less thought.