This work explores and develops philosophical themes that underlie an argumentative conception of law (which the author presented a few years ago in his Course of legal argumentation), that is, how to understand law, legal knowledge, justice or philosophy itself Of law. The main thesis is that law does not consist exclusively of a set of norms, but must, above all, be seen as a social practice guided by goals and values. The author understands that the objective of the philosophy of law can not be other than social transformation. And it underlines the idea that the ambiguity of our Rights (the possibility that the legal thing is unjust, or the just, antijuridic) does not mean that there are no intrinsic values ​​to the Law or that can be dispensed with the Law in forming a project of social ideality .