One reasons not just in beliefs, but also in intentions, preferences, and other attitudes. For instance, one forms preferences from preferences, or intentions from beliefs and preferences. Formal logic has proved useful for modelling reasoning in beliefs -- a process of forming beliefs from beliefs. Can logic also model reasoning in multiple attitudes? We identify principled obstacles. Logic can model reasoning about one's attitudes -- a process of discovering attitudes -- but not reasoning in attitudes -- a process of forming attitudes. Beliefs are special attitudes in that logic can model both reasoning about beliefs and reasoning in beliefs, namely as entailment between beliefs or entailment between belief contents, respectively. This makes beliefs the privileged target of logic as applied to psychology.