Locke'un izinden gidersek, kişi sayılabilmek için birinin gerekli ölçülerde gelişmiş, hisleri deneyimleyebilen, düşünen ve faal bir zihne sahip olması gerekir.
We are not apart from the causal world. We are very much a part of it. We are causal agents: we initiate causation and our actions have effects. We are also causal patients: things are done causally to us. We are therefore both causally active and passive. Just like everything else, we have no escape from the causal web of the world.
One reason why causation interests us is because it is related to the important issue of human agency. When we act, we cause things to happen. We are the originators of new causal chains, or so we would like to think. Causation is not merely a theoretical problem, which concerns only philosophers; nor is it important just because some distant discipline depends on it. Rather, if human agency is causation, then the issue is one of immediate significance to every being who has ever done anything.
Real necessity, as far as Humeans are concerned, resides only in ‘relations of ideas’; 2 + 2 = 4 is necessary only because its truth is contained in the meanings of the ideas involved. Similarly, we can say that if today is Wednesday, tomorrow has to be Thursday. But the necessity of this truth is entirely in the words. There is no worldly necessity compelling the future.