We already know that the body is a series of organs, working together to maintain the overall function of the whole. We can point to the Brain and safely say that it contains our memories and our being. Brain injury can change your whole personality, and wipe clean your memories. We don't fully understand it, no, but i do not think anyone would argue that the Brain is not the driving force for our physical bodies and our mental domain.

Now, death to me, means the death of the Brain. Your body can die and be revived, but if the Brain dies it is over for that person. Personality and memories are lost, and the person is reduced to a mass of organic matter. I see no evidence for a soul leaving, merely the failure of the controlling organ.

Some people like to say they have three aspects: physical; mental; and spiritual. I think we have only the first two. The spiritual side is a sub-category of the mental side. Part of what makes us human is our desire to question and seek reason. It is a result of having such a large Brain, capable of complex thought. Every Society is built on our basic need for reason. People do things for a reason, so it must extend outwards and upwards, so that there is a reason for us being here? I think that misses the point. We have the most advanced Brains on the planet. We should use them to investigate the Universe around us, not fall back on to what we would like to be the case.