Whoever has passed an evening with serious melancholy people, and has observed how suddenly the conversation was animated, and what sprightliness diffused itself over the countenance, discourse, and behaviour of every one, on the accession of a good-humoured, lively companion; such a one will easily allow that cheerfulness carries great merit with it, and naturally conciliates the good-will of mankind.  No quality, indeed, more readily communicates itself to all around; because no one has a greater propensity to display itself, in jovial talk and pleasant entertainment.  The flame spreads through the whole circle; and the most sullen and morose are often caught by it.  That the melancholy hate the merry, even though Horace says it, I have some difficulty to allow; because I have always observed that, where the jollity is moderate and decent, serious people are so much the more delighted, as it dissipates the gloom with which they are commonly oppressed, and gives them an unusual enjoyment.

From this influence of cheerfulness, both to communicate itself and to engage approbation, we may perceive that there is another set of mental qualities, which, without any utility or any tendency to farther good, either of the community or of the possessor, diffuse a satisfaction on the beholders, and procure friendship and regard.  Their immediate sensation, to the person possessed of them, is agreeable.  Others enter into the same humour, and catch the sentiment, by a contagion or natural sympathy; and as we cannot forbear loving whatever pleases, a kindly emotion arises towards the person who communicates so much satisfaction.  He is a more animating spectacle; his presence diffuses over us more serene complacency and enjoyment; our imagination, entering into his feelings and disposition, is affected in a more agreeable manner than if a melancholy, dejected, sullen, anxious temper were presented to us.  Hence the affection and probation which attend the former:  the aversion and disgust with which we regard the latter.

[Footnote:  There is no man, who, on particular occasions, is not affected with all the disagreeable passions, fear, anger, dejection, grief, melancholy, anxiety, &c.  But these, so far as they are natural, and universal, make no difference between one man and another, and can never be the object of blame.  It is only when the disposition gives a propensity to any of these disagreeable passions, that they disfigure the character, and by giving uneasiness, convey the sentiment of disapprobation to the spectator.]

Few men would envy the character which Caesar gives of Cassius: 

 He loves no play,
 As thou do’st, Anthony:  he hears no music: 
 Seldom he smiles; and smiles in such a sort,
 As if he mock’d himself, and scorn’d his spirit
 That could be mov’d to smile at any thing.