There is a lot of debate in Christian circles on the question of whether forgiveness, as a Christian responsibility, ought to be conditional or unconditional: should it be conditioned on apology and repentance (for instance) on the part of the wrongdoer, or not?
I am of the opinion that forgiveness is essentially an unconditional act, it is unconditioned on the performance of expiatory acts of atonement on the part of the wrongdoer (e.g., apology, etc.), and here is one argument to that conclusion.
I draw from a passage in Jacques Derrida, On Cosmopolitanism and Forgiveness (Routledge, 2001):
Imagine, then, that I forgive on the condition that the guilty one repents, mends his ways, asks forgiveness, and thus would be changed by a new obligation, and that from then on he would no longer be exactly the same as the one who was found to be culpable. In this case, can one still speak of forgiveness? That would be too simple on both sides: one forgives someone other than the guilty one. In order for there to be forgiveness, must one not on the contrary forgive both the fault and the guilty as such, where the one and the other remain as irreversible as the evil, as evil itself, and being capable of repeating itself, unforgivably, without transformation, without amelioration, without repentance or promise? Must one not maintain that an act of forgiveness worthy of its name, if there ever is such a thing, must forgive the unforgivable, and without condition? (pp. 38-9).
The idea Derrida is here proposing is the following. It is essential to an act of forgiveness that we direct our attention to the person to be forgiven as guilty, that is, as standing before us with some kind of an invisible debt to be paid for her transgression. If we do not approach the other person as guilty then we are not engaging in forgiveness: for instance, if we come up with excuses for her action, or if we are merely ignoring it, we are not forgiving. This is standard stuff as far as the philosophical literature on forgiveness is concerned. The basic principle at work is that forgiveness presupposes outstanding guilt; if there is no guilt, there is nothing to forgive. Therefore if we forgive, we must approach the other person as guilty, holding her guilt before our mind.
But now if we insist on placing conditions on forgiveness, conditions by which the wrongdoer's character is changed and transformed, and her disposition towards us is visibly and perceptibly different from when she wronged us, how are we still approaching the guilty as guilty? In a real sense, it is an entirely different person standing before us. Now we are approached by someone who repudiates the past action, who vows to prevent its future occurrence, someone who is fundamentally on our side. This not the same person that wronged us. This person is not guilty of anything, and consequently there is nothing to forgive.
Now if you insist that I am confusing qualitative and numeric identity in all of this, you would be raising an irrelevant point, since our guide and standard in the moral evaluation of our peers is their qualitative appearance to us in the social context. I don't have immediate access to you as a substance when I talk to you or interact with you. What I have is access to the way in which you appear to me, your various perceived traits and beliefs and predispositions, etc., by which I construct a conception of yourself. It is this conception that I project on to you and which I address with moral rebuke, praise, or whatever. This is why if I change enough of my habits, beliefs, attitudes, etc. perceptibly, people will say that I've changed, that I'm a different person now. In a sense I am a different person, within the moral plane in which conditions of identity are different than on the strictly metaphysical plane.
If all this is correct, then in imposing a condition of atonement on the wrongdoer before we are to forgive, effectively we are doing what Derrida says: we are forgiving someone else other than the one who did us wrong. This is tantamount to a refusal to forgive, a refusal to approach your wrongdoer and to look upon her with kind eyes; it's a refusal to love your enemy. Or consider the same point from a more economic angle. If wrongdoing incurs a kind of invisible debt, then atonement is a way of repaying that debt. Apologies, repentance, etc., are ways of repaying the debt: "You owe me an apology," we might say. But if we condition forgiveness on the repayment of the debt, we are effectively making forgiveness impossible. What's to forgive if the debt has been paid? Therefore forgiveness is essentially unconditional.
But suppose you want to insist on the continuity of identity between a person who wronged and the person who performed atonement. In that case, it is not obvious that forgiveness should be conditioned on the performance of atonement: there is no changing the fact that this person here who stands before you, apologies and all, did you some wrong, and there can be no changing that fact, ever. The fact of the wrongdoing has been inscribed on the immutability of the past. Why should you forgive, even if atonement has been performed? What kind of payment can make up for the eternally remanent malefaction committed against your person?
But in any case insisting on identity of person is misguided, to my mind. For these reasons, then, I argue that forgiveness is an essentially unconditional phenomenon.
Now we all know that unconditional forgiveness of this sort is an incredibly difficult thing to do. In fact it seems rare is the soul who can muster up the kind of strength of will and magnanimity to forgive a person who has done her wrong without conditions or stipulations. But what follows from this? Christians ought to seek to train themselves in forgiveness until they can do that. If they have difficulty forgiving, then they ought to pray to God to help them in this respect. This can only be done through the power of the Holy Spirit; see the case of Stephen (Acts 6.5, 7.60).