Metaphysics and Ethics as natural dispositions of the human being are - in a mutually opposite way - the expression of the transcendentality of human spirit. The transcendentality is, as such, not comprehendible by our conceptions. It can be demonstrated as unavoidable only by an indirect and negative argument, in that it is necessarily presupposed in each attempt of contesting it. But from this argument cannot be deducted any content of Metaphysics and Ethics. When we attempt a positive argument by the reflection of self-awareness or by the necessity of self-assertion, we fall in an endless regress. According to Kant, Ethics is grounded in the 'pure fact of reason'. But any fact itself requires a ground. Metaphysics cannot yield this ground, according to Hume's 'razor'. On the other hand, Metaphysics cannot be founded in Ethics, as Levinas thinks, for the relation to the 'face' of an Other has no theoretical evidence. Ethics as universally obligatory is nevertheless bounded on the principle of non-contradiction of thinking, and the principle of non-contradiction can be justified only by the ethical duty to participate in the dialogue concerning the existence of truth. This mutual necessity refers to the mutual foundation of Metaphysics and Ethics. In this mutual foundation of the unconditioned principles there is the 'utopian place' of the absolute truth of Metaphysics and the absolute validity of Ethics.