In this sense, the definition of the behaviour of human beings includes both voluntary or conscious actions as well as involuntary or unconscious actions. Voluntary action includes the person's intention and will, whereas the involuntary actions exclude the persons’ intention and desires. It includes the biological actions of the body. The behaviour is studied by undertaking both the outer environmental conditions as well as the inner potential capacities of human beings. As Churchland puts it, "Instead of appealing to mental states, behaviourists proposed to explain any organism's behaviour in terms of its peculiar environmental circumstance. Or, in terms of environment plus certain observable features of the organism. Or, in terms of certain unobservable features of the organism¾ dispositions, and innate and conditioned features meet a very strict condition: they must be such that their presence or absence could always be decisively determined by behavioural test, as solubility of sugar is revealed by its actually dissolving (the behaviour) when placed in water (the environmental circumstances)."⁵ Insofar as the mental state is concerned, there are two aspects which count mostly for explaining the mind: they are the dispositional capacity as an intrinsic feature of the human beings' organic structure and the environmental condition as an outer condition in which a person is being situated.  Environment is an external condition which has a direct impact on human behaviour.