You can also tackle this issue from the perspective of somebody who already believes in the existence of the soul.
"The soul is that which gives life to the living" --a la Aquinas or Aristotle (I think).
Problem N°1: If the soul is that which gives life to the living, does the soul itself has a life of its own? In other words, is the soul alive? If the answer is 'yes', then how is it that it is alive? (is there a soul's soul?) If the answer is no, then where is it that life itself resides? Because my body is just that: my body. And a soul, on the other hand, a soul. Is life some third element in the mix? (body, soul, life?).
Problem N°2: How is it that the soul provides the living with its own life? Again, this is like the last part of the first Problem. You have a lifeless body, then a soul: where is life in all of this? The life that the soul provides for that lifeless body?
Problem N°3: That which is alive consists of body + soul. But a body does not possess life of its own. How is it that a body is alive, then, like when we say that it is 'imbued with soul'? At most you have a soul moving different parts of some inert body (Problem N°1: where is the 'life'?).
Now, on the other hand, when you say that the soul is some sort of 'conscience', I ask: a conscience of what? Isn't it conscience always the conscience of something? And if conscience is just some sort of feeling, there you have it: the soul is just a feeling... (?).