The two main narrative techniques used in Robinson Crusoe are epistolary and memoir.
The book is presented as the memoirs of Crusoe after his adventures, and incorporate his diaries into their narrative. The memoir-style is used to present a more realistic, immediate experience, rather than a third-person recounting of events that happened to other people. It also allows Crusoe to look back and comment on his earlier actions from a position of greater wisdom.
Epistolary narrative is the style of using what appear to be authentic letters or documents in the narrative. As Crusoe keeps a diary on the island, he uses entries from it to directly show his feelings at the time:
JUNE 18. -Rained all day, and I stayed within. I thought at this time the rain felt cold, and I was something chilly; which I knew was not usual in that latitude.
JUNE 19. -Very ill, and shivering, as if the weather had been cold.
JUNE 20. -No rest all night; violent pains in my head, and feverish.
(Defoe, Robinson Crusoe, eNotes eText)
By using his diary in this manner, Crusoe is able to both show his developing personal beliefs, and comment on his younger self. The diary format makes his stay on the island more believable, as it reads less like an edited and considered manuscript and more like something written on the spur of the moment.
The narrative techniques included used in Robinson Crusoe include those of realistic fiction, autobiography, and spiritual autobiography. Crusoe narrates the events of the novel from his own point of view, and he includes not only his own biographical details but also his inner emotions. For example, at the beginning of the novel, he says of his origins: "Being the third son of the family and not bred to any trade, my head began to be filled very early with rambling thoughts." The reader has access to the biographical details about Crusoe's family and has insight into Crusoe's reaction to his family. For example, when his father urges him, even to the point of tears, to settle down to a predictable and safe career such as law, Crusoe says,
I was sincerely affected with this discourse, and, indeed, who could be otherwise? and I resolved not to think of going abroad any more, but to settle at home according to my father’s desire.
Crusoe wants to follow his father's advice, but to his own chagrin, finds he cannot. The reader has access to the emotional state of the narrator during these events. To some degree, Crusoe is a bit of an unreliable narrator because, unlike an omniscient narrator, he does not always understand everything that is happening to him.
The novel is also a type of spiritual autobiography, a common type of writing in Defoe's time, as it examines the narrator's conversion from unbeliever to Christian. As Crusoe says,
I had hitherto acted upon no religious foundation at all; indeed, I had very few notions of religion in my head, nor had entertained any sense of anything that had befallen me otherwise than as chance. . . But after I saw barley grow there, in a climate which I knew was not proper for corn, and especially that I knew not how it came there, it startled me strangely, and I began to suggest that God had miraculously caused His grain to grow without any help of seed sown.
At first, Crusoe disavows God by refusing to follow his father's advice or believe in God, but when he is shipwrecked, he begins to see signs of God. For example, he senses God's presence in the way in which barley magically grows on the island. The novel follows the traditional conventions of a spiritual autobiography, in which a non-believer is shown the folly of his ways and becomes a devout Christian. The narrative techniques involve references to the main character's ever-changing relationship with God.
In addition to using autobiographical narration, Defoe uses a style of realistic narration that was similar to that used in many sea stories. For example, Crusoe narrates a storm at sea in the following way:
By noon the sea went very high indeed, and our ship rode forecastle in, shipped several seas, and we thought once or twice our anchor had come home; upon which our master ordered out the sheet-anchor, so that we rode with two anchors ahead, and the cables veered out to the bitter end.
This type of nautical story goes back even to the time of Homer and the Odyssey, and Defoe also wrote tales of piracy. In this type of narration, the main character sets sail and faces the perils of the sea, which often help him become a better person. The narrative presents realistic details of life on the sea, and the plot revolves in part around nautical events.