Do we have a sentient soul? I would say no, and as proof I point to those suffering from Alzheimer's. That disease robs a person of their memory, so by the time of death they have lost much of who they were. If the sentient soul exists, it must be able to remember, otherwise it cannot retain the traits that make the individual unique. It should retain all the memories of our life. Yet those with Alzheimer's forget who they are. How is this possible if we possess a sentient soul? If we cannot retain memories in this life, how will we do so in the next?

What about those with major brain damage from stroke or mishap? Part of their brain died, and whatever that part contained, it's now gone. Is their soul now split? Did part of it "move on" with the dead part of the brain?