“He fixed his definition thus: reflection is the possibility of the relation, consciousness is the relation, the first form of which is contradiction. He soon noted that, as a result, the categories of reflection are always dichotomous. For example ideality and reality, soul and body, to recognize – the true, to will – the good, to love – the beautiful, God and the world, and so on, these are categories of reflection. In reflection, these touch each other in such a way that a relation becomes possible. The categories of consciousness, on the other hand, are trichotomous, as language itself indicates, for when I say I am conscious of this, I mention a trinity. Consciousness is mind and spirit, and the remarkable thing is that when in the world of mind or spirit one is divided, it always becomes three and never two. Consciousness, therefore, presupposes reflection. If this were not true it would be impossible to explain doubt. True, language seems to contest this, since in most languages, as far as he knew, the word ‘doubt’ is etymologically related to the word ‘two’. Yet in his opinion this only indicated the presupposition of doubt, especially because it was clear to him that as soon as I, as spirit, become two, I am eo ipso three. If there were nothing but dichotomies, doubt would not exist, for the possibility of doubt lies precisely in that third which places the two in relation to each other. One cannot therefore say that reflection produces doubt, unless one expressed oneself backwards; one must say that doubt presupposes reflection, though not in a temporal sense. Doubt arises through a relation between two, but for this to take place the two must exist, although doubt, as a higher expression, comes before rather than afterwards.”

Johannes Climacus (1841) p. 80-81
1840s, Johannes Climacus (1841)