In this paper, I argue that genuine ethical deliberation, and hence ethical agency, is incompatible in principle with the possession of determinate practical prescriptions concerning how best to act in a concrete ethical situation. I make this argument principally by way of an analogy between gameplay and ethical deliberation. I argue that trivially solved games of perfect information (the example I use is tic-tac-toe) are, or become, in some sense unplayable for the individual for whom the game is trivially solved. The reason for this, I suggest, is that there ceases to be space within the game for the distinction between that individual being a better and being a worse player of the game. I then use this example as an occasion to reflect on the kind of epistemic indeterminacy that appears to be a condition of genuine ethical deliberation. 1 | INTRODUCTION Under certain conditions and to some extent, ignorance undermines moral responsibility. This is one of the oldest and most widely held intuitions about agency, and the debate about what kind of ignorance is morally exculpatory (and under what conditions and to what extent it is exculpatory) shows no sign of abating. In this paper, however, I propose to discuss a threat to agency from the other end of the epistemic spectrum. The issue with which I will be concerned is the kind of knowledge that is compatible with ethical deliberation and agency and with the kind of knowledge that is not so compatible. More specifically, I will argue that deliberation and agency are incompatible with the kind of knowledge that would provide its possessor with determinate prescriptions concerning how best to act in a concrete ethical situation. And I do so principally by way of an analogy. The analogy is one between game playing and ethical deliberation. I argue that trivially solved games of perfect information (the example I use is tic-tac-toe or noughts and crosses) are, or become, in some sense unplayable for the individual for whom the game is trivially solved. I claim that if the game is solved for you, if you know with perfect or near perfect reliability what you ought to do in the game, you cannot play the game anymore. It may look like you are playing