How does one reconcile the concept of many lifetimes with the Christian perspective? One must first realize that Truth and all related phenomena are an aspect of universal existence and can have many names. So whilst there is no concept of reincarnation from the Christian viewpoint, it does not necessarily mean it does not exist as a phenomena. It is simply not called reincarnation. In Christianity, on the other hand, we have concepts such as the realms of heaven, hell, and purgatory, upon which a soul enters depending upon one's performance in the physical world. While from the Christian perspective this is viewed from the purview of a single lifetime, the very concept of purgatory suggests something that is akin to samsara, the cycle of life and death in Buddhism. For one who does not gain entry into heaven and yet is not relegated to the hellish realms re-enters a mid-cycle of purgatory. And in such a way, the concept of reincarnation and the stages of hell, purgatory, and heaven describe similar phenomena albeit through different vantage points. 

Our physical world contains much of the dimensions of purgatory through which souls enter to evolve until we achieve entry to heaven. In this world the soul has a critical purpose to evolve through life lessons and decisions that purify our spirits, until we re-enter that which is our heavenly home, our original state of being. Now whether that is achieved in multiple lifetimes or in a single lifetime is where the various religious paths differ. However, the end result, of returning to our heavenly state of bliss, or nirvana, is the same whether it takes multiple lives or a single one. And in all paths, the potential to achieve this state through a single lifetime remains entirely within the realm of possibility. 

The beauty of Truth is that it is the Truth no matter what name or from what vantage point one chooses to view the Truth. Whether or not one believes in reincarnation does not mean it does not exist. Whether one believes one can reach salvation in multiple lives or in one does not negate the possibility of both. Whether one chooses to acknowledge the existence of a Creator, does not negate the existence of a Creator, by whichever name He has chosen to be known to you. And yes it is the divine will of the Creator which paths are given to us, although it is our will to choose whether to follow.