a An oak tree is a tree. What does this mean given the statement about trees and their color?
B
b What color is the Hulk?
C
c Consider your answers in Part A and Part B.
A
a Yes, see solution.
B
b No, see solution.
C
c No, see solution.
Practice makes perfect
a We are told that all trees are green. This means that yes, an oak tree must be green. If all trees are green, and an oak tree is a tree, then it naturally follows that an oak tree must be green.
All trees are green ⇒
An oak tree is green
b Now we are asked if anything that is green is a tree. Obviously, no, not all green things are trees. The color green is not exclusive to trees. There are lots of things that are green like cars, sweaters and the Hulk. Therefore, one cannot say that anything green must be a tree.
All trees are green
⇏
Anything green must be a tree
c We are asked if the statements All trees are green and All green things are trees are the same. The first statement only considers trees and their color, while the second statement talks about everything that is green, which we know from Part B is not exclusive to trees.
As the picture shows, a frog is green but not a tree. Therefore, these statements have different meanings.
