 The curious quality of second-order logic is that the truth of a sentence such as \(\theta_{\textrm{CH}}\) in a big enough model of the empty vocabulary is equivalent to the truth of the Continuum Hypothesis in the set-theoretical universe. By the same technique almost any set-theoretical statement can be turned into a sentence of second-order logic, the truth of which in a big enough model of the empty vocabulary is equivalent to the truth of the statement in the set-theoretical universe. Somehow second-order logic manages to read the background set theory correctly. Does this mean that second-order logic is set theory in “sheep’s clothing”?