His out-of-body thinking starts with his source epistemology. He gets the language for his epistemology from Husserl. Phenomenology starts with a “principle of principles” that “primordial presence to intuition is the source of sense and evidence, the a priori of a prioris.”
This means that “the certainty, itself ideal and absolute, that the universal form of all experience (Erlebnis), and therefore of all life, has always been and will always be the present. The present alone is and ever will be. Being is presence or the modification of presence. The relation with the presence of the present as the ultimate form of being and of ideality is the move by which I transgress empirical existence, factuality, contingency, worldliness, etc.” [Speech and Phenomena, 53-54.]

However, the choice of the words “present” and “presence” to indicate the ground of all knowledge has some very unfortunate consequences. That choice sets up a confusion between two completely different meanings of the word “presence.”
One meaning is “phenomenological presence”. This refers to the immediate access to being in the original act of knowledge. It does not refer to time at all. So, phenomenological presence might be better expressed by calling it presence-to-being. That would save it from being confused with the other meaning of “presence”, what we should call “temporal presence”, that is, the occurrence of an event at a particular moment in
time.

Derrida also calls this living presence “the now”. This reinforces the confusion between presence-to-being and occurrence-at-a-particular-moment-in-time. It is also unfortunate that Derrida uses the word “form” in the phrase “the universal form of all experience”. What he wants to refer to is the “universal basis of all experience”, which is not a form. It is an act. But this word-slippage is also quite telling, and one of the many clues in Derrida’s work that he is confusing the order of abstract concepts and the order of actual reality.

This epistemology leads to the cornerstone mistake of claiming that iterability is an a priori condition of knowing, whereas in fact iterability is an a posteriori result of knowing. An original presence-to-being (insight) occurs in time. Consequently it is repeatable. So, iterability is not “inside” phenomenological presence, it is extrinsic to it. This mistake is made all the more easy since both relationships are necessary. Once you get this, then all of Derrida’s objections to realist epistemology collapse, and his core philosophical system collapses into imaginary ashes.

I have discussed these issues at length in my article “Dealing With Derrida”, which you can find on the Radical Academy web site. http://radicalacademy.com/studentrefphilmhd1.htm

Although running down Derrida’s mistakes in his text is difficult, once you get the key point that he was dissociated, the whole pattern of his out-of-body thinking makes sense. Once you discover Derrida’s dissociation, you find it in many thinkers. There is a lot of out-of-body thinking in philosophy and social theory. Perhaps leaving one’s body is an occupational hazard for professional thinkers. Dissociation is the result of trauma, and trauma is easy to come by.

There are many sources of insight into dissociation. I recommend Trauma and the Body (2006) by Pat Ogden et al. as a start.