Which of the following criticisms of formal logic was used to critique rationalism? (Check all that apply)

a. Formal logic assumes that all variables have a fixed, unchanging essence
b. Formal logic requires that variables be listed as X1, X2, X3, etc.
c. Formal logic assumes that it is possible to create an experimental group and a control group that only differ in one respect
d. Formal logic can only show that a conclusion follows from an initial assumption, but this does not show the initial assumption is true