John Locke claimed that any theories on the soul were not based on the available evidence and should therefore be discarted. For instance, he claimed there is no way to know whether, for instance, God gave our material body the capacity to think or whether God added an immaterial soul to our body with the capacity to think. No matter who you are, there is no way distinguish between these two hypotheses with the evidence at hand.
We have the ideas of matter and thinking, but possibly shall never be able to know whether any mere material being thinks or no. [It is] not much more remote from our comprehension to conceive that God can, if he pleases, superadd to matter a faculty of thinking, than that he should superadd to it another substance with a faculty of thinking.