Here’s an excerpt from Conrad’s Author’s Note:
“This story, which I admit to be in its brevity a fairly complex piece of work, was not intended to touch on the supernatural. Yet more than one critic has been inclined to take it in that way, seeing in it an attempt on my part to give the fullest scope to my imagination by taking it beyond the confines of the world of the living, suffering humanity. But as a matter of fact my imagination is not made of stuff so elastic as all that. I believe that if I attempted to put the strain of the Supernatural on it it would fail deplorably and exhibit an unlovely gap. But I could never have attempted such a thing, because all my moral and intellectual being is penetrated by an invincible conviction that whatever falls under the dominion of our senses must be in nature and, however exceptional, cannot differ in its essence from all the other effects of the visible and tangible world of which we are a self-conscious part. The world of the living contains enough marvels and mysteries as it is; marvels and mysteries acting upon our emotions and intelligence in ways so inexplicable that it would almost justify the conception of life as an enchanted state. No, I am too firm in my consciousness of the marvelous to be ever fascinated by the mere supernatural, which (take it any way you like) is but a manufactured article, the fabrication of minds insensitive to the intimate delicacies of our relation to the dead and to the living, in their countless multitudes; a desecration of our tenderest memories; an outrage on our dignity.”The ghost of the previous captain (a man called Mr. Burns) is described by one of the inmates of the ship in these words: “His face in the full light of day appeared very pale, meagre, even haggard. Somehow I had a delicacy as to looking too often at him; his eyes, on the contrary, remained fairly glued on my face. They were greenish and had an expectant expression."