Notes on: Lecture 1 Heidegger, M. The Principle of Reason translated by Reginald Lilly, Indiana University Press 1991, Lectures held in 1955-1956,

[The principle of sufficient reason is considered to be one of the foundational principles of our thinking. Even thought the principle of identity, of the excluded middle, and of non-contradiction were discovered earlier, the principle of sufficient reason is on of the main grounding principles. With respect to its foundational position we can ask different questions:

1. Is the principle of sufficient reason equiprimordial (gleichursrpruenglich) to the other principles or has it a higher status?
2. Is the principle of sufficent reason a merely logical principal or a synthetic a priori?

We will discuss the first question with regard to Heidegger's first lecture on the principle of sufficient reason.]

Heidegger Notes

[Logic as the foundation of all our thoughts is hidden within us; as Heidegger will call it later as an abyssal structure that provides the realm of our thinking. We can say that the principles of logic need attention to be formulated and that there sentence structure is not what they are.]

Heidegger writes: "Centuries were needed for the principle to be stated as a principle" In German he emphasizes that it took 2000 years "für das Setzen des Satzes" and he answers it: "Answer: because our relation to the ovious is always dull and dumb. The path to what lies  under our nose is always the furthest and hence the most difficult path for humans." (5) So what is ontologically most important is usually considered to be furthest. An so he asks: "What reason is there for the principle of reason?"

[In other lectures Heidegger pointed out that the foundational principle is a principle in itself: Der Grundsatz des Denkens ist selbst ein Satz (7)] Heidegger points out the puzzling structure of this principle: "What the principle of reason posits, and how it posits it - the manner in which it is, strictly speaking, a principle - is what makes it incomparable to all other sentences." (7)  So the principle of reason has a significant role among all sentences.

Remarks on the principle of identity: Heidegger points out that the principle of identity should not be confused with the formulation A=A. Saying that something ist identical means not that it "is being equal to itself" (8). [Moreover it seems that the equation expresses a relation that cannot be there, if it were identical.]

Heidegger says it more precisely:
"In identity, the same plays the role of a reason or basis for belonging-together. In identity reason shows itself to be the basis upon which and in which the belonging- together of distinct things rests. (8)

So the principle of identity demonstrates an internal belonging to each other. [vgl. Hegel's analysis of the Wesen and Unwesen - With respect to Hegel we pointed out that there are severe problems with atomism in a common representationalism. The Hegelian question is directed toward the object that is many in one. How can different properties be regarded as being One?]

[We can take the first lecture as the questioning of what we are going to analyze.]

So Heidegger first analyzes the sentence in which a principle is usually uttered. Moreover, Heidegger sees the German connotation of Satz = Setzen (principle --> positing). He says:

"It is indeed equally necessary to clarify what a sentence [Satz] is. According to grammar, a simple sentence consists of the connection of the subject of a sentence with a predicate. The predicate is to agree with the subject and is predicated of the subject. But what is meant by "subject"? . . . "that which is  lies present as the ground for statements about something."

[Therefore we need a clarification of Reason before in order to grasp what it means to have an underlying structure that cannot be taken away].

[Remark: Also Kant runs into this reasonable structure when he searches for the highest identity. As a result it comes to the question whether we are dealing with a completed identity as, for example, Kant assumed it for the I-think as the underlying structure of everything.

This also leads us to the question whether everything is reasonable grounded.