Albus,
You fault me for not coming to a decision regarding our arrangement. You call me indecisive; I believe, rather, that I am calculating. My reticence toward committing myself to such an endeavour must be understood not as cowardice, but as yet another move in the chess game that is our plan. You would not jostle the man deep in thought over the most effective way to capture the other's piece. I do not understand why you do this to me. Have I not served you well? Do I not deserve your unwavering trust, such as you have declared to me? All I ask is for more time. Not to stall, but to weigh each option carefully, as I would any delicate potion ingredient. My virtues are not compassion, nor kindness, nor empathy. They are, in fact, my steadfastness, my logic, and my sense of observation; in short, I am dictated by my head, not my heart. There was a time when I believed that you appreciated me for this. That you saw in me the ability to lead my students on the path of knowledge. Now, you demonstrate to me that you wish me to change all of what you have seen in me. You wish me to become impulsive, rash, quick to the draw, to display Gryffindor courage -- and perhaps foolishness -- in defiance of my inherent Slytherin traits. I cannot abide by your demands. I remain loyal to you, my teacher, my leader. This does not mean that I can comply with every one of your wishes. I know that you, being wiser than any living wizard, understand this. I must ask then, do you truly believe me to be capable of what you are asking of me? You are asking me, in short, to give up. To give up that which I have presented to my colleagues, that of the loyal servant, that of the warrior against the Dark Lord's ways. You are asking me to comfirm their darkest suspicions, that I am in fact loyal only to the Dark Lord. That I am the Judas in your midst, the betrayer. The hangman, when I am in fact the condemned. No, I cannot, will not, commit that act. You ask of me too much, and it is this that belies my head, and injures my heart. I have a cold exterior, of this I am aware; but I am yet a man, a man who has witnessed the struggles of the good and the pure and has felt a fire in his belly, an urge to join the brave who only wish for a better world. Please, Albus...to destroy you would be to destroy myself. Please, place your demands on a more hardy soul, for I am weaker than you think me to be. Do not ask this of me, I beg of you.
Faithfully, Severus Snape