The subject term of the conclusion refers to all members of that category, but the same term in the premises refers
only to some members of that category.
This is fallacious by definition, since it does not respect syllogistic structure.
All communists are subversives, and all communists are critics of capitalism, therefore, all critics of capitalism are subversives.
The subject term in the conclusion is 'critics of capitalism'. The conclusion refers to all such critics. The premise that 'all
communists are critics of capitalism' refers only to some critics of capitalism; there may be other critics who are not communists.
Show that there may be other members of the subject category not mentioned in the premises which are contrary to the conclusion.
For example, from the above, one might argue, "While it's true that all communists are critics of capitalism, it is also true that
Thomas Jefferson was a critic of capitalism, but Thomas Jefferson was not a subversive, so not all critics of capitalism