| | You know, in the case of the growing shadow, it seems to depend on the observer.
If you are the kind of observer which Joe describes -- young and naive -- then it would appear that making the inference about the shadows would be 100% inductive. However, if you are the kind of observer that, say, Merlin is -- then for you it is somewhat less than a 100% inductive inference: part of it is deductive. This is because some of the steps required for making the inference in the first place are so inextricably intertwined with such an immense background of real knowledge which you already possess -- that you can leap past a lot of the induction that would be required from a so-called naive observer.
Harriman talks about shadows in The Logical Leap, and he mentions some of the things (p 16- ) you would have to be able to integrate in order to get into the position to make the inference that light travels in straight lines:
1) the inference that light travels at all (which can be made after measuring its speed by studying the eclipses of the moons of Jupiter)
2) ... but (1) requires prior inferences, "including those that led to the heliocentric theory"
3) ... (1) also requires inferences about "how light behaves in relation to lenses and mirrors" (needed to invent the telescope in the first place, bringing Jupiter's moons into view for the 1st time)
4) ... but this just proves -- beyond the shadow of a doubt (forgive the pun!) -- that light travels; it does not prove that light travels in straight lines
5) the inference that the 'straight lines' hypothesis sufficiently explains the shape of shadows (and little else, perhaps nothing else, does this task)
6) ... but (5) requires prior inferences, "namely: light does cast shadows behind any opaque object it strikes
7) ... but (6)) requires prior inferences, such as "'candles cast shadows behind people' and 'shadows appear on sunny days.'"
8) ... but (7) requires prior conceptualization -- i.e., the conceptualization of the shadow
9) ... but (8) requires prior inferences, such as "'The dark areas, in contrast to the objects they abut, have not tactile properties'"
10) the inference that "the dark areas are not objects, but rather an effect produced when an object blocks light"
11) ... but (10) requires prior inferences related to one entity blocking another entity (e.g., "Walls resist hammering hands.")
That's at least 11 steps, just to get into the position to be able to say that light travels in straight lines -- something which you need to first know in order to know why it is that a shadow gets longer later in the day!
Ed
(Edited by Ed Thompson on 1/28, 6:24pm)
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