How come you cannot make inferences from Venn Diagrams?

Question

I was working with Sorites, and instead of making inferences and checking their validity with the Venn Diagram, I first created the Venn Diagram and drew inferences from that. I was told by my professor that you cannot do this, that Venn Diagrams are only to be used for checking the validity of inferences, NOT for making inferences. Why is this?

This was in a Logic class, which is why I put it in the Philosophy section. Thank you in advance for your help.

Answer 1

For Sorites, venn diagrams are used in two different ways.

First, they are used to uncover the intermediate conclusion(s). In this sense, the venn diagram does reveal an inference that previously was only implied.

The original conclusion to the sorties is explicit (it is not merely implied as are the immediate conclusions).

So once the original explicit conclusion is reached - it is compared to the venn diagram in order to test the last chain of the sorites for validity.