The way in which we conceptualise, deal with, or process, our emotions, and the importance we give to emotions themselves, have both been influenced by various schools of philosophical thought. What follows is a brief outline of some of these influences. Some of the ideas such as catharsis seem to apply very closely to emotional processing, others do not directly apply to processing but to emotions more generally.
Cleanthes of Assos
Chrysippus of Soli
Zeno of Citium (344-262 BCE)
Everything other than one’s character, or rationality, is ultimately indifferent. This is the ideal of the Stoic philosophers that lead them to reject the emotional life. The argument goes something like this:
We should give up the idea that anything matters that is beyond our control. Having control is the most important part of life. One thing we can control is our own character, and we can control that by deciding to be virtuous. We can always control our virtuous character; after all we could be starving to death and still be virtuous. Therefore, all else becomes indifferent: Life, health, pleasure, beauty, strength, well-functioning sense organs, wealth, reputation and their opposites, death, disease, pain, ugliness, frailty, disablement, poverty, low repute, and ignoble birth. Actually, these positive ‘indifferents’ were preferred, if circumstances permitted, but ultimately were considered as neither good nor bad.
Emotions as Judgements
For the Stoics, emotions consisted of two different types of judgement. The first judgement being that there is good or bad at hand, and the second judgement concerning the appropriateness to act. Four emotions were selected as being the most generic; distress, pleasure, fear, and appetite. So, in the case of distress, harm is judged to be at hand (in the present) and it is judged appropriate to have a sinking feeling. With pleasure, benefit is judged to be at hand (in the present) and an expansion (of the mind) is felt. With fear, a judgement is made that something bad is at hand (in the future) and it is appropriate to avoid it. With appetite, benefit is at hand (in the future) and it is judged that it should be reached for.
A Rejection of Emotion
The Stoics, however, are persuaded that these judgements (emotions) are actually false. Their reasoning is that part of each judgement presupposes that things are either good or bad. This position clearly contradicts the Stoic theory of indifference outlined above, and so the ideal state that the Stoic sage must aspire to is one that is free from emotions.
Aristotle (384 – 322 BCE) The notion of catharsis
Aristotle’s theory of catharsis was presented in defence of the poets, who had been attacked by Plato in The Republic , and banished from the ideal society. Plato believed that the Arts were dangerous because they incited the passions and overshadowed Reason. For Aristotle, stirring up the emotions, far from being dangerous, was actually beneficial in a number of ways
“We also say that music should be used to procure not one benefit but several. It should be used for education and for catharsis and thirdly as a pastime, to relax us and give us rest from tension.” Politics  The idea here is that through the Arts (music or tragedy for example), the audience will have their emotions roused and any excess of emotion can be expunged. Although the process of emotional catharsis is cross-referenced, in the Politics, to a now lost text, Aristotle hints at the purgative qualities of the process by employing a medical analogy: “For some people are possessed by this movement, and when they use melodies which make the soul frenzied we see them restored by the sacred melodies as if they got healing and catharsis. All must get a sort of catharsis and be lightened together with pleasure.” Politics 
René Descartes(1596-1650): The mind/body problem
Through his sceptical meditations, Descartes was doubtful as to most of the beliefs about the external world we receive through the senses. What is presented to us courtesy of the senses might appear perfectly plain, however, but we might actually be being deceived. Objects in the distance can occasionally deceive us, we could be suffering from hallucinations, we could mistakenly believe we are awake when in fact we are asleep, or we could be being tricked by a wicked demon.
However, this ‘Cartesian doubt’ leads to a conclusion that becomes, for Descartes, certain. ‘No demon could be deceiving me, however wicked and cunning, if I did not exist.’ Put simply the argument runs, cogito ergo sum (I think therefore I am).
Mind and body are separate
Descartes was so convinced of the special nature of the mind that he saw it as something separate from the body:
“…although I certainly do possess a body with which I am very closely conjoined; nevertheless, because, on the one hand, I have a clear and distinct idea of myself, in as far as I am only a thinking and unextended thing, and as, on the other hand, I possess a distinct idea of body, in as far as it is only an extended and unthinking thing, it is certain that I, that is, my mind, by which I am what I am, is entirely and truly distinct from my body, and may exist without it.” Sixth Meditation 
Descartes goes on to argue that there is a vast difference between the body and the mind and body in that the former is divisible whereas the latter is indivisible. He is already convinced that as a thinking thing he is whole, entire and indivisible. Conversely, he argues that corporeal things, however small, are always divisible. This, says Descartes, should be argument enough, “this would be sufficient to teach me that the mind or soul of man is entirely different from the body, if I had not already been apprised of it on other grounds.” Sixth Meditation 
But what about emotions?
Cartesian dualism runs into difficulties, however, when it tries to explain emotions. If the self is an incorporeal, ‘thinking substance’ entirely distinct from the body, how do we account for the feelings and emotions that seem to be so intertwined with our bodies?
Reason is the slave of the passions
Hume’s philosophy of emotions is interesting in that it challenges the high station of reason and questions the inferiority of emotions. In his ‘A Treatise of Human Nature’ Hume devotes the second of three books to the Passions. In Part III, ‘Of The Will and Direct Passions’, Hume summarises the ‘slave/master’ position between reason and emotion, “[n]othing is more usual in philosophy, and even in common life, than to talk of the combat of passion and reason, to give the preference to reason, and assert that men are only so far virtuous as they conform themselves to its dictates.” 
Hume sets out to prove that reason, alone, can never be a motive to any action, and that reason can never oppose passion in the direction of the will. He asks us to consider mathematics, mechanics or arithmetic. These arts are useful tools, granted, and they are used in every profession, but of their own they are abstract and demonstrative procedures only, and can never influence our actions. With the prospect of pain or pleasure, Hume argues, reason can only direct the emotions to the relationships between the objects associated with the original emotion. In other words, if we are not affected (indifferent) by objects in the first place, then we cannot know anything about their cause and effect relationships. Hume’s point is that, “as reason is nothing but the discovery of this connexion, it cannot be by its means that the objects are able to affect us.” Of The Will and Direct Passions 
Similarly,Hume infers that if reason alone cannot produce action then neither can it oppose the passions in the direction of the will. Nothing can oppose the impulse of passion except another, contrary impulse. If this impulse stemmed from reason then reason could have an influence on the will. It must be able to cause as well as block acts of will. However, Hume has already argued that reason alone cannot produce volitions, “[t]hus it appears, that the principle, which opposes our passion, cannot be the same with reason, and is only called so in an improper sense. We speak not strictly and philosophically when we talk of the combat of passion and of reason. Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.” Of The Will and Direct Passions ”