The doubt is this:
“The purpose of reincarnation and karma is reformation of the soul over the span of many lifetimes. But if I don’t remember my previous lifetimes, I don’t know what karma is punishing or rewarding me for – therefore how can it be effective?”
This doubt assumes that only things one consciously remembers can affect one’s life and attitude. Ask any psychologist and you will quickly realize this is very untrue. In fact most patients are effected by events they cannot (or, really will not) consciously recall, at least not accurately.
The patient’s conscious mind intentionally blurs, represses, and hides specific memories. Why? Because to remember the event would cause a transformation that is too drastic and dramatic for their conscious mind to face. This is why the vast majority of people do not often have (or recognize) very clear memories from their previous lifetimes. To do so would case a transformation too jarringly drastic and all-devouring for them to accept.
If I tangibly recalled all my past lives, the importance of many (sometimes all) aspects of my current life might suddenly reduce to sub-atomic size. “You mean I have already done everything like this a million times before? And it never quenched the thirst? You mean I have already had a million children, wives, husbands, lovers, fans, dollars, etc. etc.?” And not to mention: “You mean I always die!?” The transformation that the blunt, unmetered dawning of this information would have upon a common mind would be like forcing a lightning bolt’s voltage through a delicate circuit board: it would fry.
The vast majority of people are not ready or willing to completely embrace reality at this very moment. Therefore the conscious universe (“supersoul”) intentionally hides most of reality from our view, and shows us only that which we are ready and willing to accept.
Yet the conscious universe does not abandon us entirely to our wayward hallucinations. It wishes to gradually and gently prod us in the direction of remembering and accepting reality. This is why karma exists. Through it, we can connect to themes from previous lifetimes without violating the principle that we cannot recall what we are unwilling to recall. These subconscious connections allow reality to gradually and gently dawn upon us over a course of millions of lifetimes.
Those who are allowing this treatment to be effective are those to whom the confusions karma begins to become quite plain and simple, and for whom access to the vault of memories from past lives is beginning to crack open.
Those very, very rare and few souls who have reached the goal of treatment and are cured of “ahamkara” (conception of the identity as fundamentally uncentered on and cut off from divinity); they are those upon whom karma has no affect at all, and for whom all of the past, present and future is within their conscious comprehension.