Firstly, I'll admit that this is for a school assignment but is ridiculously abstract. I'm supposed to "unpack" the argument stated below, which is to identify the premises and conclusion of the argument, while also listing down any implicit premise or conclusions to make the argument valid. This is no need to evaluate the argument. The argument is a passage adapted from David Lindberg’s Theories of Vision from Al Kindi to Kepler (pg 10).
A body that is seen does one of two things: either it sends something (an image) from itself to us and thereby gives us an indication of its character, or if it does not itself send something, it waits for some sensory power to come to it from us. The first alternative is unacceptable for it would be impossible to determine the size of an object from an image coming from it to us, for the image of a very large mountain would have to shrink drastically in order to enter the pupil. Since the mountain will not come to the observer, the observer must go to the mountain; he must, that is, send forth his sensory power to perceive it.
Thus far, I've made the following argument diagram/steps and would like to know if they are correct or missing anything (which I believe to be the case):
- The image of a very large mountain would have to shrink drastically in order to enter the pupil. (Explicit premise)
- If a very large mountain shrinks itself drastically in order to enter the pupil, then the image we receive is inaccurate. (Implicit premise) (Not sure if this is correct)
- A very large mountain cannot shrink itself drastically in order to enter the pupil. (Implicit premise) (Not sure if this is correct)
- It would be impossible to determine the size of an object from an image coming from it to us. (Follows from 1 & 2/3) (Explicit intermediate conclusion)
- A body that is seen does one of two things: either it sends something (an image) from itself to us and thereby gives us an indication of its character, or if it does not itself send something, it waits for some sensory power to come to it from us. (Explicit premise)
- The first alternative (it sends something (an image) from itself to us and thereby gives us an indication of its character) is unacceptable. (Follows from 4) (Explicit intermediate conclusion)
- The observer must send forth his sensory power to perceive an object. (Follows from 5 & 6) (Explicit conclusion)