2002, Immanuel Kant, W. Hastie (translator), The Metaphysics of Morals, in The Philosophy of Law: An Exposition of the Fundamental Principles of Jurisprudence, page 29 (originally published in 1797)
According to these Categorical Imperatives, certain actions are allowed or disallowed as being morally possible or impossible […].
2001, Roger Scruton, Christopher Janaway, German Philosophers: Kant, Hegel, Schopenhauer, Nietzsche, page 75:
Categorical imperatives do not typically contain an 'if. They tell you what to do unconditionally. They may nevertheless be defended by reasons.
