are stacked against him.

More than any more exalted themes, the story of exactly how a lone man manages to stay alive and thrive on an untamed island has captured imaginations for many generations. We identify with Crusoe because, like us, he is an ordinary human. The novel has no supernatural elements: no magical fairies or sprites are going to come to save him. We put ourselves in his shoes and keep reading to find out how Crusoe will use nothing but his wits and hard work to beat the odds. The wealth of detail that Defoe offers about what Crusoe exactly does to survive makes the story believable and interesting.

Later, as Crusoe settles in and his mere survival is no longer a question, new adventure comes as he witnesses native cannibals from a neighboring island landing on the shores of "his" island. This adds a new level of adventure, and we thrill as Crusoe saves Friday.

Plot is important, and even though Crusoe spends much of the novel alone, there is always something going on to catch our interest. The message or theme of the adventure is never to give up, because you don't know what you have inside you or what the world (or God, in terms of how Crusoe understands his experiences) has in store for you until you put your all into the struggle for life.

When Robinson Crusoe first embarks upon his epic adventures, it’s fair to say that self-awareness is not really his strong point. He has no idea as to how much he’s upset his father by defying his wishes and heading off to sea. Nor does he subsequently have the slightest notion as to how much physical and psychological damage is done to the slaves in whom he trades, not even when he himself ends up in captivity.

The world is too much with Crusoe and he too much with it for him to be able to learn anything from his adventures on the high seas. It’s only when he fetches up on a remote desert island that he finally starts developing an insight as to who he is and who he could become if only he would change his selfish ways.

The isolation of life on the island, with its deprivation of human companionship, makes Crusoe understand what it is to be human. Forced back on himself, Crusoe’s adventures on the island take place within himself as much as outside him. Over time, he experiences considerable growth and personal development, which lead him toward maturity and wisdom. It is this process, one could argue, that represents a greater and more compelling adventure in the story than anything that happens at sea.

Much has been written about themes other than adventure hidden in the depths of Defoe's Robinson Crusoe novel. However, the overall prevailing theme is that of an adventure genre. 

By definition the adventure genre is dominated by danger, action, risks and excitement. They take place in unusual settings unlike that which people encounter everyday. The action is fast paced and extraordinary compared to daily life. 

Robinson Crusoe contains all of these elements and more. The adventure begins with the wreck of Crusoe's ship and his immediate action to salvage materials that he can use to survive. Each day Crusoe must solve problems and find new ways to survive the elements, hunger and occasional savages. Further adventures have him taming and domesticating wild goats, learning to grow food to survive, meeting a converting a savage named Friday into a companion and helping a group of sailors and captain who arrive to restore order to their ship. They in turn, take Crusoe back home. 

Although the book has many deeper themes, it can also be read as a simply adventure story.  After all, if you think about it, Robinson Crusoe encounters a huge variety of adventures in the course of this book.

Just think about some of the things that happen to him.  He is captured and has to live some years as a slave until he can make a daring escape.  He then becomes a rich man in Brazil.  Then comes the long adventure -- he goes off, and is shipwrecked on the island.

Once he is on the island, his attempts to survive constitute an adventure.  He is having to survive in a difficult environment using only his ingenuity and what he could salvage from the ship.  As if this conflict with nature weren't enough, he then has to face cannibals.  He finally gets off the island and he has a fight with a huge pack of wolves.

In other words, there's all sorts of action and adventure in this book.

Slavery is treated as a normal aspect of life for those, like Crusoe, who ventured out into the wide seas. It is a hazard anyone aboard a ship faces, no matter what his race or nationality. The young Crusoe himself, who did not heed his father's warning that this would happen, is soon on board a ship captured by the Moors. He is enslaved. He writes about it both as not as bad as he had feared, yet still terrible enough to overwhelm him:

the usage I had there was not so dreadful as at first I apprehended ... I ... was kept by the captain of the rover as his proper prize, and made his slave, being young and nimble, and fit for his business. At this surprising change of my circumstances, from a merchant to a miserable slave, I was perfectly overwhelmed

However, ever resourceful, Crusoe does manage to escape and reunite with western Europeans. When his fortunes change, he takes no lesson from his distress as a slave but simply takes advantage of the resources provided by his new plantation in Brazil to buy a slave and a European indentured servant to supplement the one provided by his captain. Interestingly, he does not distinguish between the slave and the indentured servants: all are "bought."

for the first thing I did, I bought me a negro slave, and an European servant also—I mean another besides that which the captain brought me from Lisbon.

Nevertheless, the plight of the white Europeans "bought" by Crusoe is far less dire than that of the Negro, as Europeans would serve him only for a limited time.

When he discovers that cannibal "savages" are rowing to his island. Crusoe dreams of enslaving some of them:

Besides, I fancied myself able to manage one, nay, two or three savages, if I had them, so as to make them entirely slaves to me, to do whatever I should direct them, and to prevent their being able at any time to do me any hurt.

That doesn't work, but when he saves Friday, the young "savage" feels a great indebtedness to him and functions as his slave. Friday's plight, like that of the European indentured servants, is helped by racial politics. Crusoe softens to him because he looks "European" in many ways:

he had all the Sweetness and Softness of an European in his Countenance too, especially when he smil'd. His Hair was long and black, not curl'd like Wool; his Forehaed very high, and large, and a great Vivacity and sparkling Sharpness in his Eyes. The Coulour of his Skin was not quite black, but very tawny; and yet not of an ugly yellow nauseous tawny, as the Brasilians, and Virginias, and other Natives of America are; but of bright kind of a dun olive Colour, that had in it something very agreeable; tho' not very easy to describe

Thematically, in the broadest sense, being master or slave is matter of luck. Sometimes you are on the bottom of the wheel of fortune and must adjust, as Crusoe did, to slavery, but sometimes you are on top and can enslave others. This is depicted as the byproduct of an amoral universe in which might makes right, and how much power you have amassed at a given moment determines whether you live in ease or toil. However, complicating this is the fact that looking more "savage" implicitly made the slavery situation worse for some and looking (or being) "European" made it better for others.

In Robinson Crusoe, the title character’s attitude toward slavery is one of acceptance. Crusoe was operating as a slave trader, accompanying a ship from Brazil to Africa, when he himself was captured and enslaved. He also owned a slave, Xury, and upon selling him, worried about his subsequent treatment—but sold him nonetheless. The excesses of specific slave owners, not the system itself, are of concern to Crusoe.

It is Crusoe’s relationship with Friday that has drawn the most attention, as it occupies a sizable portion of the book. Crusoe’s generally colonialist attitude, declaring himself king of the island, is consistent with his paternalist attitude toward Friday. Convinced that he has superior knowledge and should teach Friday, his first lessons are about the word “master,” which Friday must call him. In the absence of a monetarily-based financial system on the island, and because there is no evidence that Friday previously was considered anyone’s property, Crusoe cannot technically be a slave-master to Friday in that he does not purchase him. Regardless, Crusoe’s attitude encourages and praises the alleged subservience in Friday’s behavior from the very moment they first meet:

I smiled at him, and looked pleasantly, and beckoned to him to come still nearer; at length he came close to me, and then he kneeled down again, kissed the ground, and laid his head upon the ground, and taking me by the foot, set my foot upon his head; this it seems was in token of swearing to be my slave for ever; I took him up, and made much of him, and encouraged him all I could (emphasis added).

Given that the novel is entirely told from Crusoe’s perspective, the reader never hears Friday’s version of this initial meeting. The idea that innately submissive attitudes were characteristic of dark-skinned people, who were grateful to white Europeans for rescuing them, was a foundation of colonialist politics and a standard trope in contemporary literature.

It has been noted that, along with not overtly criticizing slavery in this novel, Daniel Defoe rarely did so in his other published works. To the contrary, Defoe had invested in Britain’s Royal African Company, and he wrote of slavery as an economic necessity. His stated oppositions were largely economic, criticizing private slave traders who interfered with the profitable operation of the official royal company. In some writings, he endorsed owner’s violent control over slaves as their “property,” which was necessary to increase their labor.

Keane, Patrick J. 1994. Coleridge’s Submerged Politics: The Ancient Mariner and Robinson Crusoe. Columbia: University of Missouri Press.

Slavery, being a normal part of everyday life in the 1700s when Robinson Crusoe was written, is treated as simply a fact and not a moral issue. Early in the book Crusoe himself is captured and sold into slavery, but is treated well and is able to escape; from this, he takes the position that he cannot stand to be made to serve, but does not apply this attitude to other slaves. When Friday appears on the island, Crusoe initially treats him as a child-like savage, but soon discovers that Friday is as innately intelligent as himself, and is both impressed and somewhat humbled. While he continues to treat Friday like a servant, he does not treat him as a slave; in fact, Crusoe's initial defense of Friday against the cannibals is indicative of his personal convictions.

Even after his initial shipwreck, Robinson Crusoe is obsessed with travel and takes another ship to Africa. This is the most important journey he takes, for it allows him to gain valuable knowledge that will serve to keep him alive later in life:

...I got a competent knowledge of the mathematics and the rules of navigation... in a word, this voyage made me both a sailor and a merchant; for I brought home five pounds nine ounces of gold-dust for my adventure.

Of course, this rise must be coupled with a fall, and so Robinson is promptly capture by pirates and sold into slavery. His owner does not seem to be a brutal or cruel man, but simply a slaveowner.

...I was in hopes that he would take me with him when he went to sea again... But... when he went to sea, he left me on shore to look after his little garden, and do the common drudgery of slaves about his house.
(Defoe, Robinson Crusoe, eNotes eText)

Even as a slave, Robinson yearns for ocean travel; it is as if he would be content to live on the ocean even as a slave as long as he is not reduced to common labor, which, of course, he is. This lust for travel and hatred of being confined leads to his escape, and then to his most important shipwreck that leads to his long solitude on the island. Robinson's lust for personal freedom allows him to trick his captors, and the seafaring knowledge he gained earlier gives him the ability to sail away in a manner that throws off pursuit.

His initial "adventures" takes a lot of the young Robinson Crusoe's passion out of him, so most of the relevant quotes come in the first two chapters. For example:

My father... designed me for the law; but I would be satisfied with nothing but going to sea.

Because of his older brother who was killed in action during the Franco-Spanish war, young Robinson wants to sail the ocean and seek adventure. His father, having lost two sons already, cautions him against it, but since they are a wealthy family, Robinson avoids learning a specific trade and becomes a practical dilettante.

He told me it was men of desperate fortunes on one hand, or of aspiring, superior fortunes on the other, who went abroad upon adventures... that these things were all either too far above me or too far below me.
(Defoe, Robinson Crusoe, eNotes eText)

Of course, this sort of speech only fuels Robinson's desire for adventure. He feels sympathy for his father, but his own desires are paramount, and so he jumps a ship heading for London. From this point, all events seem designed to keep him from sailing further, but he is stubborn, and continues to sail even through a shipwreck and slavery to pirates; his most famous shipwreck comes only after years of rising and falling fortunes. Similar quotes are often tinged with regret, as the older and wiser Robinson Crusoe looks back on his life and examines his choices with a more objective eye.