if-then
Explanation
This comic plays on the logical structure of "if-then" statements, but applies it to the very different domain of romantic and sexual communication.
In the first panel, one person asks another "Why did you take your pants off?" The second person, sitting at a table, responds simply: "You're eating lasagna." The first person, visibly confused and disturbed, says "But--" and then "I am getting SUCH mixed signals from you."
The caption below the comic spells out the logical joke: "Turns out 'we should incorporate eating into sex' does not imply 'we should incorporate sex into eating.'" This is a direct reference to the logical fallacy of affirming the consequent, or more colloquially, confusing the direction of an implication. If the couple agreed to bring food into the bedroom, one partner has incorrectly concluded that this also means bringing nudity to the dinner table. In formal logic, "If sex, then eating" does not mean "If eating, then sex" -- the converse of a conditional statement is not logically equivalent to the original.
The humor operates on two levels. First, there is the inherent absurdity of someone stripping down at dinner because lasagna is being served, treating any meal as an automatic trigger for intimacy. Second, there is the nerdier, more structural joke about logical implication: the comic literalizes what happens when someone confuses "A implies B" with "B implies A." The title "if-then" directly flags this as a joke about conditional logic.
The "mixed signals" line is particularly funny because the confused partner is the one sending them -- they have constructed their own bizarre logical chain and are baffled that their partner does not follow it. The comic takes a common relationship complaint ("mixed signals") and reveals that the signals are only mixed because one person is applying flawed reasoning to an agreed-upon premise.