The History of Rasselas, Prince of Abyssinia, Samuel Johnson's "philosophical romance" concerns the desire of the eponymous protagonist to discover whether it's possible for mankind to attain happiness. Although he himself has lived a life of unbroken serenity amidst boundless luxuries in a beautiful setting, both aptly and ironically named Happy Valley, the twenty-six-year old prince has become sated with this existence, and is anything but a happy man.

After numerous failed efforts to interest himself in local affairs, Rasselas seeks to escape from Happy Valley but finds every path has been blocked. He meets Imlac, a visiting sage, who describes for the prince the pain and oppression of a world yet unseen by him, with the tale of his own vicissitudes therein. Listening to this narrative makes the prince even more eager to see the outer world himself, and with the wise man's guidance, digs a tunnel through the mountains to escape. The prince's favorite sister Nekayah, as dissatisfied as her brother, joins them on their journey, accompanied by her maidservant, Pekuah.

As they travel through the world, the initial astonishment of the royal siblings fades as Imlac instructs them in the endlessly varied manners of the human race. Rasselas continues in his search to solve the mystery of happiness, but finds it as frustratingly elusive as he had in Happy Valley. Neither the pursuit of sensual pleasures, the possession of wealth, nor the attainment of learning seem to guarantee his intangible objective. Nekayah, who has spent much of her time in observing domestic life, also is saddened to find a status quo of discontent.

At Imlac's suggestion, Rasselas and Nekayah join him in visiting a pyramid, while leaving the claustrophobic Pekuah to rest in their tent. After reflecting on the folly of the royal vanity that built such a monument, the trio emerge into the light to find that Pekuah has been seized by Arab horseman. Rasselas is eager to give chase, but Imlac reminds him that they are no match for Pekuah's captors. Nekayah is grief-stricken.

The search for Pekuah continues as Nekayah languishes, but after seven months, the princess if overjoyed when they learn that her maid is alive. She is being held by an Arab chief who demands a ransom for her return, which they immediately pay.

Order restored, the travelers contemplate the future. When Rasselas declares to Imlac that he is considering a solitary life devoted to learning and literary pursuits, the sage tells him about an erudite astronomer friend, seemingly perfect in every way, who one day quietly revealed to him his godlike control of the universe, and his intention to pass this power on to Imlac. Such madness, he warns, is the potential danger of a solitary life. Fascinated by this astronomer, the women demand that Imlac arrange a visit, and over a period of months in their company, the man gradually regains his sanity.

But, what ultimately does Rasselas determine to be the source of human happiness? Perhaps this quote comes closest to Johnson's belief:

Such, said Nekayah, is the state of life, that none are happy but by the anticipation of change: the change itself is nothing; when we have made it, the next wish is to change again. The world isn't yet exhausted; let me see something tomorrow which I never saw before.

It is the custom in Abyssinia for the sons and daughters of the emperor to be confined in a remote place until the order of succession to the throne is established. The spot in which Rasselas and his brothers and sisters are confined is a beautiful and fertile valley situated between high mountains. Everything needed for a luxurious life is present in the valley. Entertainers are brought in from the outside world to help the royal children pass the time pleasantly. These entertainers are never allowed to leave, for the outside world is not to know how the royal children live before they are called on to rule.

It is this perfection that causes Rasselas, in the twenty-sixth year of his life, to become melancholy and discontented. He is unhappy because he has everything to make him happy; he wants more than anything else to desire something that cannot be made available to him. When he talks of his longing with an old philosopher, he is told that he is foolish. The old man tells him of the misery and suffering of the people outside the valley and cautions him to be glad of his present situation. Rasselas, however, knows that he cannot be content until he sees the suffering of the world.

For many months, Rasselas ponders about his desire to escape from the valley. He takes no action, however, for the valley is carefully guarded and there is no chance for anyone to leave. Once he meets an inventor who promises to make some wings for him so that he can fly over the mountains, but the experiment is a failure. In his search for a way to escape, his labor is more mental than physical.

In the palace, there is a poet, Imlac, whose lines please Rasselas by their intelligence. Imlac also is tired of the perfect life in the valley, for in the past he traveled over much of the world. He observed the evil ways of humankind and learned that most wickedness stemmed from envy and jealousy. He noticed that people envy others with more worldly goods and oppress those who are weak. As he talks, Rasselas longs more than ever to see the world and its misery. Imlac tries to discourage him, for he believes that Rasselas will long for his present state if he ever sees the violence and treachery that abound in the lands beyond the mountains.

When Imlac realizes he cannot deter the prince, he agrees to join him in his attempt to leave the perfect state. Together the two men contrive to hew a path through the side of a mountain. When they are almost ready to leave, Rasselas sees his sister Nekayah watching them. She begs to accompany the travelers, for she also is bored with the valley and longs to see the rest of the world. She is Rasselas’s favorite sister, so he gladly allows her and her maid, Pekuah, to join them.

The four make their way safely through the path in the mountainside. They take enough jewels with them to supply them with money when they reach a city of trade. They are simply dressed, and no one recognizes them as royalty. In Cairo, they sell some of their jewels and rent a magnificent dwelling. They entertain great people and begin to learn the customs of people different from themselves. Their objective is to observe all possible manners and customs so that they can make their own choices about the kind of life each wants to pursue; but they find many drawbacks to every form of living.

Rasselas and Nekayah believe that it is necessary only to find the right pursuit to know perfect happiness and contentment. Imlac knows that few people live by choice, but rather by chance and the whims of fortune. Rasselas and Nekayah, however, believe that their chance birth at least gives them the advantage of being able to study all forms of living and thus to choose the one most suitable for them to pursue. So it is that the royal pair visit with persons of every station. They go into the courts and the fields. They visit sages of great fame and hermits who isolate themselves to meditate. Nowhere do they find a person completely happy and satisfied; everyone desires what another has, and all think their neighbors more fortunate than they are.

Only once does Rasselas find a happy man: a philosopher who preaches the doctrine of reason. He states that by reason, a person can conquer passions and disappointments and thus find true happiness. When Rasselas calls on the sage the following day, however, he finds the old man in a fit of despair. His daughter died in the night, and the reason that he urged others to use fails completely on the occasion of the philosopher’s own grief.

Imlac and Nekayah spend long hours discussing the advantages of one kind of life over another. They question the state of marriage as compared with celibacy, and life at court as compared with pastoral pleasures, but at no time can they find satisfactory solutions for their questions. Nowhere can they find people living in happiness. Imlac suggests a visit to the pyramids so that they might learn of people of the past. While they are in a tomb, Pekuah is stolen by Arabs, and it is many months before she is returned to Nekayah. Pekuah tells her mistress that she spent some time in a monastery while she waited for her ransom, and she believes that the nuns found the one truly happy way of life.

Their search continues for a long period. Often they think they find a happy person, but always they find much sorrow in the life they think so serene. After a visit to the catacombs and a discourse on the soul, Nekayah decides that she will cease looking for happiness on earth and live so that she might find happiness in eternity.

The Nile floods the valley and confines them to their home for a time. The four friends discuss the ways of life that promise each the greatest happiness. Pekuah wishes to retire to a convent; Nekayah desires knowledge more than anything and wants to found a woman’s college where she can both teach and learn; Rasselas thinks he wants a small kingdom where he can rule justly and wisely; Imlac says he will be content to drift through life, with no particular goal. All know their desires will never be fulfilled, and they begin to look forward to their return to the Abyssinian valley where everyone seems happy and there is nothing to desire.