Human agency is constituted by reasons. Behavior is action, if guided by reasons. But how are we to conceive the Effect of Reasons? And how is this compatible with our scientific world view? I shall discuss three characteristics of reasons: normativity , objectivity, and non-algorithmicity. Social facts play an important role for practical reasons and although they are only constituted by social practices, they are objective, what implies their realistic interpretation. This leads to the question how theoretical and practical reasons relate. I shall end with a discussion of the (metaphysical) status of reasons.