The only objective evidence is that a dead body is not conscious. Therefore, consciousness belongs to a functional body of a living being (human, animal, tree, algi, virus, any). >> As we go down to simpler and simpler live forms, consciousness turns into chemical reaction, e.g., virus. It does not have a consciousness where a brain is required. I do not think it is difficult to understand unless someone ties him/herself into religious knots. Think simple.
Buddha is generally not wrong. Yes, consciousness depends on the conditions. There should be someone to observe and something to observe. The observer should have all the paraphernalia for observation, etc. My homage to my guru, Gautama, the Buddha.