so there are two stages in the existence of an emotion. the first stage occurs when some part of the nervous system is set into motion by some cause; literally, some event, whether entirely external to the body (e.g., something in the room) or internal (one part of the body affecting another, e.g., the rise in heart rate or the excretion of sweat) has causal contact with some part of that nervous system and as such, sets it into motion and causes it to become active. at this fundamental level you could call this a ‘disturbance’, but don’t think of it in its usual terms; this doesn’t necessarily mean there is a conflict or opposition… only that the inertia of some part has been changed by the activity of another part, either external or internal. so essentially emotion in this first stage is what happens when stimulation occurs as a result of an exchange of chemical and/or physical forces. as a consequence of some particular chemical law, for instance, potassium particles become charged and then move along the axon… which then results in another series of actions resulting from their particular natural laws, etc.
the second stage occurs in becoming aware of the emotion, or the body set into motion. but this stage, this being aware, is never complete and only a partial awareness. what we do is attribute to some complex of causes the quality of being the sole proprietor of the effect, the experienced emotion, but can never account for the totality of causes that participate in producing that effect. so our knowledge here is always incomplete. for example, i take a caffeine pill and experience a rise in energy level. of course, the caffeine contributes, as a cause, to this rise in energy level, but it isn’t the only cause making this effect possible. same with emotions like fear, anger, happiness - as changes in the motion and activity of various parts of the nervous system; it isn’t only because your homeboy didn’t pay you back that you’ve become angry… or only because your boyfriend bought you flowers that you feel happy.
in addition to us being unable to know of all the causes responsible for a particular emotion, part of this uncertainty leads us necessarily to believe we have freewill (see the pigeon superstition clip in the ‘spinoza’s god’ video i posted in ecmandu’s ‘god is simple’ thread). in our immediate experience of what we call ‘willful volition’, we experience more forcefully than anything else our ‘choosing’, and so associate with this ‘decision’ the ruling causal event that forced the action to happen. as spinoza once said: we believe ourselves to have freewill because we are ignorant of the causes of our actions. instead what happens here is like the pigeon superstition effect. because the ‘thought’ always and without exception precedes the action, we learn to believe the thought causes the action, when in reality it did not. just as the pigeon believes his flapping his wings is what causes the food pellet to be released, we believe our ‘thinking to raise our arms’ is what causes our arms to raise.
another way to understand why this is so is to think about the evolution of simple-to-complex language using animals. we don’t say a paramecium has freewill, but we do say a human being does. but why? well because over vast periods of time we have developed language as another kind of behavior that incidentally, and in a rather peculiar way, operates in parallel to other behaviors. our nervous systems just happen to produce the mediating thought (in language) before the action that follows… and so we experience this phenomenologically as evidence of freewill. but the thought is already part of a system of complex causes that are operating irrespective of the final stages of thinking and acting. but because these are the only two stages we can be aware of, we isolate them and call them the final causes.
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that bit about the ‘increase of human activity’ making more conflict possible and therefore increasing both the experience and composition of possible emotions essentially means; the complexity and sophistication present in our interactions with both the environment and other people increases the range of possible stimuli made available to act as causes. so for example, you’re no longer just a caveman who’s biggest concern is keeping the fire going in the rain. now, say, you’re a conservative mother of three who’s nervous about a job interview, is undecided about taking an experimental drug for a blood-sugar disorder you have, is suspicious of your husband cheating on you, needs to find a new groundskeeper to do the yard work, is considering becoming a vegetarian after watching a video on the horrors of slaughter farms, and any other comparatively complicated circumstances you find yourself in. so the novelty as well as the frequency of emotional experience is greatly increased, compared to the life you lived as a caveman.
in spinozea terms (deleuzean as well), there are more possible assemblies of causes and effects to be realized and put into motion, mapping the degree of activity both externally and internally.