The field of experience divides into an objective world and a subjective world, and includes the native conviction that every other person is associated with subjective experiences. It would follow from this conviction that every other person would be associated with a field of experience that similarly divides into an objective world and a subjective world. To put it another way, just as the field of experience encompasses the conviction that it is associated with a unique conceived person inhabiting the objective world, so all perceived people inhabiting the objective world are, by extension, conceived to be associated with fields of experience. It is, as it were, an inductive inference based on a single sample, and so it is possible to call this default assumption into question, and this is known as the "problem of other minds".
There is nothing contentious about accepting on face value the instinctive conviction that all people are associated with minds, and perhaps nothing too contentious about extending that assumption to all anthropoids on grounds of structural similarity. But to go much further becomes controversial. It might be argued that there must be a threshold at some point on the phylogenetic scale, the location of which would depend upon structural similarity or dissimilarity, but this claim can be nothing more than a matter of prejudice given that even our grounds for imputing minds to other people cannot be given empirical support. The bottom line is that there is no justifiable argument for denying minds to even non-anthropoids - e.g. I could extend the claim without inconsistency to all mammals, and indeed to all animals throughout the phylogenetic scale, right down to the single-celled protozoa. Furthermore, if there are no logically consistent grounds for denying minds to animal cells then why not to plant cells? I could even continue on to the cellular organelles, and further still to the molecules that comprise them. And if the argument applies to molecules then why should it not apply to atoms, and even to sub-atomic particles? The particular view to which this line of reasoning leads was championed by Alfred North Whitehead and has been given the name panexperientialism. A common argument arraigned against this view confuses mind with cognition - an argument that rejects the idea that e.g. cells might be associated with minds on the grounds that a single cell is incapable of cognition. It should be clear, however, that this is an incoherent objection - a mind need not encompass cognition, or even emotions. The constituents comprising any mind that might be associated with a single cell need not be as rich as those accompanying a person.
The problem arises as to how a collection of minds, each mind being associated with an object within a cohesive system of objects, can combine to yield a single over-arching mind that is associated with the system as a whole - e.g. cells combine to yield an organism, so how do the minds of the cells combine to yield the mind of the organism? This objection is known as the "combination problem" and was first raised by William James as "the mind dust problem". I present a defence of panexperientialism with a proposed solution to the combination problem here: