Moral laws and theorums are universal and categorical based upon their empiric content and irregardless of their particular form. This empiric content exists in strict consonance with sensation and reason, and is invariably reflected in, and borne out by, application, experience, and practice.
The fundamental personal moral law, or Categorical Imperative, of pure practical reason is: Think as much and as well as possible. Then obey and act upon your rational thoughts and conclusions, neither lying to yourself, nor evading yourself or reality.
The fundamental social moral law, or Categorical Imperative, of pure practical reason is: Treat others as you want them to treat you. But also respect their differences from you in taste, prejudice, opinions, and thought -- and act accordingly.
But even without this last fundamental social moral law, man can easily know himself and be free -- just by heeding the personal law. And all such laws can and should be heeded because every "Thou ought" implies and reveals an equivalent "Thou can."
The rational postulates of the practical reason are that god doesn't exist but is still evil, and that the human soul is both mortal and material. But the universe is still good and great, life is still noble and heroic, and men are still born naturally free and happy. Pure practical reason insures all of this.
