Derrida.....the supplement and play issues

One thing I was unsure about was the center. After going over it though I feel I have a much better understanding of it and how Derrida discusses the center. The center is the source of truth, the origin. According to Derrida you have to rethink the center. The center is absent so you must rethink it to understand it. He is not saying there is no center he is saying it is something “within the structure and outside it. The center is at the center of the totality, and yet, since the center does not belong to the totality, the totality has its center elsewhere” (R&W p.196). Strauss’ idea on ethnology is, you believe in something (the center) prior to (outside of) the system to validate it. The center stabilizes the system. This gives understanding to Derrida’s quote on how the center is both within and outside the totality at the same time.
Another part of the center is the metaphysics of presence. This is the study of nature of reality. The study of nature of reality as something that’s present to us. Heidegger feels philosophers do not question what gives a being presence they just assume, to be is to be present. Derrida attacks the center of knowledge as presence. Derrida feels that western society views speech as more privileged over writing. He disagrees and feels both are equal. He is deconstructing the idea of knowledge as presence. His idea of play is a disruption of presence. I liked how in class play was described as a way to understand revolution, it makes you understand it and not the world has just gone crazy. Play to Derrida resists the stabilizing force. The stabilizing force is the center.
Another point that we discussed was the supplement. I am not as sure about this as the other points though. I understand that the supplement is a surplus and is a substitute for something lacking. The supplement substitutes for a lost center. Derrida claims that to account for an absent center one replaces it. You mask the absence of the center to ensure presence. I don’t understand though how Derrida talks about play as disrupting the presence when then he talks about ensuring the presence with the supplement. So his two ideas are to both disrupt and ensure presence????