The fallacy of composition is a type of informal fallacy which occurs when the arguer mistakenly concludes that something is true to the whole simply because it is true to some of the parts of the whole. Put differently, in the fallacy of composition, the arguer assumes that the truth of the part of the whole necessarily affects the truth of the whole. Hence, what is assumed to be true to the part of the whole is necessarily true to the whole.
Let us consider the example below.
Example 1
De La Salle University is an excellent university. I know it because De La Salle’s College of Nursing consistently tops the board exams for nursing.
As we can see, the assumption of the argument above is that what is true of the part (that is, De La Salle University’s College of Nursing) is true of the whole (that is, the entire De La Salle University). However, it is obvious that the assumption is false. It is false because the excellent performance of De La Salle’s College of Nursing in the board exams for nursing does not necessarily imply that De La Salle University is an excellent institution of higher learning. It might be the case that De La Salle’s College of Engineering performs very poorly in the board exams for engineering.
The examples below will further illustrate the fallacy of composition.
Example 2
The pink sweater is gorgeous. The purple skirt over there is smashing. I love those red shoes in the window, and how about that terrific yellow vest on the mannequin! Let us face it, it will make a great outfit for you!
Example 3
Smoking this cigarette surely cannot harm me. So, how can smoking cigarettes harm me?
Example 4
All the angles of a triangle are less than 180 degrees. Therefore angles PQR, STU, and XYZ, which compose this triangle, are less than 180 degrees.
Example 5
If anything is good for an outstanding and crucial industry, such as the steel industry, then it would be good for the country as a whole.