There are various modes of and reasons for happiness, but human beings widely though not universally have agreed that it are forms of happiness that make life worthwile. Those who did no agree on such a proposition usually did not do so because they believed happiness is an illusion or because they supposed that it is better to be morally good (in some sense) than to be happy.

1. Aristotelian happiness: There is a fine book by Wladyslaw Tatarkiewicz, "Analysis of Happiness" that is a serious, well-written, intelligent and informative study of the concept and opinions about it. To quote his analysis, which follows Aristotle mostly:

"Happiness means lasting satisfaction.
Thus happiness has to be defined as 1) complete, 2) lasting, 3) satisfying, and 4) touching the whole of life." (p. 8)

As Tatarkiewicz himself immediately proceeds to point out, the problem is that none of these four marks have a high chance of being satisfied in any one's life, or at least not to a large extent. As he says:

"There is, however, a way out of this dilemma. A distinction has only to be drawn between ideal and actual happiness." (p. 9)

This is true and makes some sense, though on the whole it seems the demand that happiness requires lasting satisfaction touching the whole of life requires too much of "the whole of life", for there are many chances for misfortune and misery in any human life.

2. Gibbon on happiness: There is a lot that may be said about happiness and misery. Here is an instructive quotation from Gibbon's "The Decline and Fall of the Roman Empire" (in which one also may learn that "History is little else but the register of the crimes, follies and misfortunes of mankind"). It concerns an opinion of an Islamic caliph of Spain of the house of the Ommiades, of ca. 800:

In the West the Ommiades of Spain supported with equal pomp the title of commander of the faithful. Three miles from Cordova, in honour of his favourite sultana, the third and greatest of the Abdalrahmans constructed the city, palace and gardens of Zehra. Twenty-five years, and above three million sterling, were employed by its founder: his liberal taste invited the artists of Constantinople, the most skilful sculptors and architects of the age; and the buildings were sustained or adorned by twelve hundred columns of Spanish and African, of Greek and Italian marble. The hall of audience was encrusted with the curious and costly figured of birds and quadrupeds. In a lofty pavilion of the gardens of one of these basins and fountains, so delightful in a sultry climate, was replenished not with water, but with the purest quicksilver. The seraglio of Abdalrahman, his wives, concubines, and black eunuchs, amounted to six thousand three hundred persons: and he was attended to the field by a guard of twelve thousand horse, whose belts and scimitars were studded with gold.

In a private condition our desires are perpetually repressed by poverty and subordination; but the lives and labours of millions are devoted to a despotic prince, whose laws are blindly obeyed, and whose wishes are instantly gratified. Our imagination is dazzled by the splendid picture; and whatever may be the cool dictates of reason, there are few among us who would obstinately refuse a trial of the comforts and the cares of royalty. It may therefore be of some use to borrow the experiences of the same Abdalrahman, whose magnificence has perhaps excited our admiration and envy, and to transcribe an authentic memorial which was found in the closet of the deceased caliph.

"I have now reigned above fifty years in victory or peace; beloved by my subjects, dreaded by my enemies, and respected by my allies. Riches and honours, power and pleasure, have waited on my call, nor does any earthly blessing appear to have been wanting to my felicity. In this situation I have diligently numbered the days of pure and genuine happiness which have fallen to my lot: they amount to FOURTEEN; - O man! place not thy confidence in the present world!""

Thus the text. Two obvious difficulties are how one defines "the days of pure and genuine happiness" and next how one counts and recognizes them, all in rational terms, next to the problem that individual temperaments may differ a lot. Gibbon also has, as often, a beautiful and personal note to the above, of which I cite the end:

If I may speak of myself (the only person of whom I can speak with certainty), my happy hours have far exceeded, and far exceed, the scanty numbers of the caliph of Spain; and I shall not scruple to add, that many of them are due to the pleasing labour of the present composition.

Gibbon seems to be right and it seems to me that that there are probably good biological and biochemical reasons, even if they are at the present stage of knowledge largely unknown, why people, if they are free from pain, free from hunger, free from fear, and have a sound mind in a healthy body, therefore and thereby at least will feel well (disregarding those born with a melancholic constitution, as also happens). For if it were otherwise, there would be many more human suicides then there are.

In any case, this is a useful fact that seems to hold for the fast majority of men: For those who are free from pain, hunger, fear and memories of suffering, life feels well.

3. Happiness and society: One reason why happiness is quite important politically, socially, religiously and ethically is that most of the "crimes and follies" of mankind (see above) are strongly correlated with personal unhappiness: If you feel truly happy or joyous, there is no felt reason to kill or persecute others (if you are not a sadist).

• The harm, misery and suffering that human beings cause other human beings tends to be caused by unhappy human beings.

4. Happiness and pleasure: According to J.S. Mill

"Happiness is desirable, and the only thing desirable, as an end; all other things being desirable as means to that end"

and

"Actions are right in proportion as they tend to promote happiness"

These are the basic tenets of Millsian utilitarian ethics. The second statement can be regarded as a definition of "right action", and seems to presuppose the first statement.

One problem with the first statement is what happiness is, and for Mill the answer to that is that in practice happiness comes down to pleasure. The further problem is then that while some pleasures seem worse than other pleasures of precisely the same strength, the Millian approach gives no logical means to explain that apparent fact, and indeed logical reasons to deny the apparent fact.

Another problem is that happiness seems to be the feeling one has if one believes one has reached some end one had, and that it is thus not pleasure in general, but the specific pleasure connected with success, and making an effort, and running risks.

This makes happiness a special kind of feeling related to ends and actions: Any end one has poses a desire to be satisfied, and to satisfy an end generally requires a series of actions and decisions, all of which will have some risk of failing, and all of which require some trouble and effort. The general feeling of satisfaction one has when realizing an end one had accordingly falls apart in the pleasures associated with the end, and the happiness associated with succesfully reaching an end.

Upon this definition, happiness is not "the only thing desirable", but merely the special feeling that accompanies realizing some desire one has, that usually is proportionate to both the importance one attaches to the end, and the trouble and risks one took to reach the end. Also, on this view happiness is not desirable, except in the sense that one desires to be successful in acting towards ends,  since it are the ends one has that are desirable for one, while happiness is the feeling one has if one is successful in realizing an end.

5. Happiness and power: It seems that men (and women, and children) do not so much want happiness as that they desire to do as they please: They want to do as they desire, first and foremost, and often choose for pleasure, but not necessarily so.

This was very well expressed by Sophocles:

"The fairest thing of all is to be just;
The best to live without disease; most sweet
Power to win each day the heart's desire."
   (Quoted in Bowra, "The Greek Experience", p. 92)

In a similar vein there was the ancient Greek inscription at Delos:

 Most noble is that which is justest, and best is health;
 But pleasantest is it to win what we love.

It is not happiness nor pleasure that people seek, but power - the ability to do as they please when they please. And indeed, it is true that the main motive for this is that power gives happiness, which need not be pleasure but may be any feeling of well-being produced by seeing an end one has satisfied.

It is noteworthy, not only logically speaking, that this is second order, in the sense that it is a desire about one's desires, and that it can be defined thus if one wants to conflate happiness and power:

• One is happy if one does what one desires to do if and when one desires.

And obviously, since this is so for each and all, and all seem to aim at happiness thus defined, it follows cooperation and agreement are  necessary for human society.