Achebe does not take his eyes from me, and I stare back at him. The face is familiar and marked with the heavy lines of ageing that one would expect to find on a 72-year-old man's face. But Achebe's lines are graceful whorls which suggest wisdom. He leans back now and looks beyond me and through the window at the snowy landscape.

We are sitting in his one-storey house in upstate New York, deep in the wooded campus of Bard College. For the past 13 years, Achebe has been a professor at this well-known liberal arts college, which has had writers such as Mary McCarthy and Norman Mailer on the faculty. His house is decorated with African art and artifacts, but the landscape and the climate could not be further removed from Nigeria and the world of Achebe's fiction and non-fiction. As though tiring of the wintry landscape, Achebe turns and returns to our conversation.

"The man would appear to be obsessed with 'that' word."

"Nigger."

Achebe nods.

"He has an admiration of the white skin. It is the whiteness that he likes, and he is obsessed with the physicality of the negro."

Again Achebe falls silent, but this time he lowers his eyes as though suddenly overcome with fatigue. I continue to look at him, the father of African literature in the English language and undoubtedly one of the most important writers of the second half of the 20th century. What I find difficult to fathom is just why Conrad's short novel, Heart of Darkness, should exercise such a hold on him?

Achebe has taught term-long university courses dedicated to this one slim volume first published in 1902. As long ago as February 1975, while a visiting professor at the University of Massachusetts in Amherst, Achebe delivered a public lecture entitled "An Image of Africa: Racism in Conrad's Heart of Darkness ". The lecture has since come to be recognised as one of the most important and influential treatises in post-colonial literary discourse. However, the problem is I disagree with Achebe's response to the novel, and have never viewed Conrad - as Achebe states in his lecture - as simply "a thoroughgoing racist". Yet, at the same time, I hold Achebe in the highest possible esteem, and therefore, a two-hour drive up the Hudson River Valley into deepest upstate New York would seem a small price to pay to resolve this conundrum.

Achebe's lecture quickly establishes his belief that Conrad deliberately sets Africa up as "the other world" so that he might examine Europe. According to Achebe, Africa is presented to the reader as "the antithesis of Europe and therefore of civilisation, a place where man's vaunted intelligence and refinement are finally mocked by triumphant bestiality".

Achebe sees Conrad mocking both the African landscape and the African people. The story begins on the "good" River Thames which, in the past, "has been one of the dark places of the earth". The story soon takes us to the "bad" River Congo, presently one of those "dark places". It is a body of water upon which the steamer toils "along slowly on the edge of a black and incomprehensible frenzy".

According to Achebe, Conrad's long and famously hypnotically sentences are mere "trickery", designed to induce a hypnotic stupor in the reader. Achebe drafts in the support of "the eagle-eyed English critic FR Leavis", who many years ago noted Conrad's "adjectival insistence upon inexpressible and incomprehensible mystery" whose cumulative effect is to suggest that poor Africa is inexplicable.

But it is when Achebe turns to Conrad's treatment of African humanity that he is most disparaging of Conrad's vision. He quotes from the moment in the novel when the Europeans on the steamer encounter real live Africans in the flesh:

"We are accustomed to look upon the shackled form of a conquered monster, but there - there you could look at a thing monstrous and free. It was unearthly, and the men were - No, they were not inhuman. Well, you know, that was the worst of it - this suspicion of their not being inhuman. It would come slowly to one. They howled and leaped, and spun, and made horrid faces; but what thrilled you was just the thought of their humanity - like yours - the thought of your remote kinship with this wild and passionate uproar. Ugly. Yes, it was ugly enough; but if you were man enough you would admit to yourself that there was in you just the faintest trace of a response to the terrible frankness of that noise, a dim suspicion of there being a meaning in it which you - and you so remote from the night of first ages - could comprehend."

These people are "ugly", but what is even more disturbing is that they are in some way also human. A half-page later, Conrad focuses on one particular African, who, according to Achebe, is rare, for he is not presented as "just limbs or rolling eyes". The problem is that the African man is, most disturbingly, not "in his place".

"And between whiles I had to look after the savage who was a fireman. He was an improved specimen; he could fire up a vertical boiler. He was there below me, and, upon my word, to look at him was as edifying as seeing a dog in a parody of breeches and a feather hat, walking on his hind legs."

Those critics who have defended Heart of Darkness against charges of racism have often pointed to both the methodology of narration and Conrad's anti-colonial purpose. The narrator of the novel is Marlow, who is simply retelling a story that was told to him by a shadowy second figure. However, in his lecture Achebe makes it clear he is not fooled by this narrative gamesmanship, or the claims of those who would argue that the complex polyphony of the storytelling is Conrad's way of trying to deliberately distance himself from the views of his characters.

"...If Conrad's intention is to draw a cordon sanitaire between himself and the moral and psychological malaise of his narrator, his care seems to me to be totally wasted because he neglects to hint, clearly and adequately, at an alternative frame of reference by which we may judge the actions and opinions of his characters. It would not have been beyond Conrad's power to make that provision if he had thought it necessary. Conrad seems to me to approve of Marlow..."

Achebe is, however, aware of Conrad's ambivalence towards the colonising mission, and he concedes that the novel is, in part, an attempt to examine what happens when Europeans come into contact with this particular form of economic and social exploitation. In the lecture he remembers that a student in Scotland once informed him that Africa is "merely a setting for the disintegration of the mind of Mr Kurtz", which is an argument that many teachers and critics, let alone students, have utilised to defend the novel. But to read the book in this way is to further stir Achebe's outrage.

"Africa as setting and backdrop, which eliminates the African as human factor. Africa as a metaphysical battlefield devoid of all recognisable humanity, into which the wandering European enters at his peril. Can nobody see the preposterous and perverse arrogance in thus reducing Africa to the role of props for the break-up of one petty European mind?"

Achebe has no problem with a novel that seeks to question both European ambivalence towards the colonising mission and her own "system" of civilisation. What he has a huge problem with is a novelist - in fact, an artist - who attempts to resolve these important questions by denying Africa and Africans their full and complex humanity.

During the two-hour drive up the Hudson River Valley through a snow-bound and icy landscape, I thought again of my own response to the novel. There are three remarkable journeys in Heart of Darkness. First, Marlow's actual journey up-river to Kurtz's inner station. Second, the larger journey that Marlow takes us on from civilised Europe, back to the beginning of creation when nature reigned, and then back to civilised Europe. And finally, the journey that Kurtz undergoes as he sinks down through the many levels of the self to a place where he discovers unlawful and repressed ambiguities of civilisation.

In all three journeys, Conrad's restless narrative circles back on itself as though trapped in the complexity of the situation. The overarching question is, what happens when one group of people, supposedly more humane and civilised than another group, attempts to impose themselves upon their "inferiors"? In such circumstances will there always be an individual who, removed from the shackles of "civilised" behaviour, feels compelled to push at the margins of conventional "morality"? What happens to this one individual who imagines himself to be released from the moral order of society and therefore free to behave as "savagely" or as "decently" as he deems fit? How does this man respond to chaos?

Conrad uses colonisation, and the trading intercourse that flourished in its wake, to explore these universal questions about man's capacity for evil. The end of European colonisation has not rendered Heart of Darkness any less relevant, for Conrad was interested in the making of a modern world in which colonisation was simply one facet. The uprootedness of people, and their often disquieting encounter with the "other", is a constant theme in his work, and particularly so in this novel. Conrad's writing prepares us for a new world in which modern man has had to endure the psychic and physical pain of displacement, and all the concomitant confusion of watching imagined concrete standards become mutable. Modern descriptions of 20th-century famines, war and genocide all seem to be eerily prefigured by Conrad, and Heart of Darkness abounds with passages that seem terrifyingly contemporary in their descriptive accuracy.

"Near the same tree two more bundles of acute angles sat with their legs drawn up. One, with his chin propped on his knees, stared at nothing, in an intolerable and appalling manner: his brother phantom rested its forehead, as if overcome with a great weariness; and all about others were scattered in every pose of contorted collapse, as in some picture of a massacre or a pestilence."

As my car moved ever closer to Bard College, I constantly asked myself, was Conrad really a racist? If so, how did I miss this? Written in the wake of the 1884 Berlin Conference, which saw the continent of Africa carved into a "magnificent cake" and divided among European nations, Heart of Darkness offers its readers an insight into the "dark" world of Africa.

The European world produced the narrator, produced Marlow, and certainly produced the half-French, half-English Kurtz ("All Europe contributed to the making of Kurtz"), but set against the glittering "humanity" of Europe, Conrad presents us with a late-19th-century view of a primitive African world that has produced very little, and is clearly doomed to irredeemable savagery. This world picture would have troubled few of Conrad's original readers, for Conrad was merely providing them with the descriptive "evidence" of the bestial people and the fetid world that they "knew" lay beyond Europe. However, by the end of the 20th, and beginning of the 21st century, Conrad's readers are living in a decolonised - indeed postcolonial - world, and Conrad's brutal depiction of African humanity, so that he might provide a "savage" mirror into which the European might gaze and measure his own tenuous grip on civilisation, is now regarded by some, including Achebe, as deeply problematic.

But is it not ridiculous to demand of Conrad that he imagine an African humanity that is totally out of line with both the times in which he was living and the larger purpose of his novel? In his lecture, even Achebe wistfully concedes that the novel reflects "the dominant image of Africa in the western imagination".

And the novel does assert European infamy, for there are countless examples throughout the text that point to Conrad's recognition of the illegitimacy of this trading mission and the brutalising effect it is having on the Africans. However, the main focus of the novel is the Europeans, and the effect upon them of their encountering another, less "civilised", world.

The novel proposes no programme for dismantling European racism or imperialistic exploitation, and as a reader I have never had any desire to confuse it with an equal opportunity pamphlet. I have always believed that Conrad's only programme is doubt; in this case, doubt about the supremacy of European humanity, and the ability of this supposed humanity to maintain its imagined status beyond the high streets of Europe. However, as I pull my car up outside Achebe's house, I already sense I had better shore up my argument with something more resilient than this.

For a moment Achebe has me fooled. He looks as though he has nodded off, but he has just been thinking. This mild-mannered man looks up now and smiles. He returns to the subject we were talking about as though he has merely paused to draw breath.

"Conrad didn't like black people. Great artists manage to be bigger than their times. In the case of Conrad you can actually show that there were people at the same time as him, and before him, who were not racists with regard to Africa."

"Who?" I ask. Achebe says nothing for a moment, and so I continue. "I find it difficult to think of any European writers who have had a benevolent view of Africa. Surely they've all used Africa as a foil."

"Well, Livingstone," suggests Achebe. "He is not a writer, but he is an explorer and Conrad admired explorers. When asked what he thought of Africans, Livingstone replied that he found them 'infuriating'. In other words, they were just like everybody else."

We both fall silent and I think back to Achebe's lecture. That Conrad had some "issues" with black people is beyond doubt. Achebe quotes Conrad who, when recalling his first encounter with a black person, remembers it thus:

"A certain enormous buck nigger encountered in Haiti fixed my conception of blind, furious, unreasoning rage, as manifested in the human animal to the end of my days. Of the nigger I used to dream for years afterwards."

Conversely, when the 16-year-old Conrad encounters his first Englishman in Europe, he calls him "my unforgettable Englishman" and describes him in the following manner:

"[His] calves exposed to the public gaze... dazzled the beholder by the splendour of their marble-like condition and their rich tone of young ivory... The light of a headlong, exalted satisfaction with the world of men... illumined his face... and triumphant eyes. In passing he cast a glance of kindly curiosity and a friendly gleam of big, sound, shiny teeth... his white calves twinkled sturdily."

However, despite Achebe's compelling "evidence", I am still finding it difficult to dismiss this man and his short novel. Are we to throw all racists out of the canon? Are we, as Achebe suggests, to ignore the period in which novels are written and demand that the artist rise above the prejudices of his times? As much as I respect the man sitting before me, something does not ring true. We both agree that Conrad was not the originator of this disturbing image of Africa and Africans. And we both appear to agree that Conrad had the perception to see that this encounter with Africa exposed the fissures and instabilities in so-called European civilisation. Further, we both agree that in order to expose European fragility, Conrad pandered to a certain stereotype of African barbarity that, at the time, was accepted as the norm. Finally, we both agree that this stereotype is still with us today. Achebe speaks quickly, as though a thought has suddenly struck him.

"You see, those who say that Conrad is on my side because he is against colonial rule do not understand that I know who is on my side. And where is the proof that he is on my side? A few statements about it not being a very nice thing to exploit people who have flat noses? This is his defence against imperial control? If so it is not enough. It is simply not enough. If you are going to be on my side what is required is a better argument. Ultimately you have to admit that Africans are people. You cannot diminish a people's humanity and defend them."

I feel as though I am walking around an impregnable fortress. However, I am losing interest in the problem of breaching the ramparts and becoming more concerned with the aesthetics of its construction.

"Which European or American writers do you feel have best represented the continent of Africa and African people?"

Achebe looks at me for a long while and then slowly begins to shake his head.

"This is difficult. Not many."

I suggest Graham Greene.

"Yes, perhaps. Graham Greene would be one because he knew his limitations. He didn't want to explain Africans to the world. He made limited claims and wasn't attempting to be too profound. After all, we can't be too profound about somebody whose history and language and culture is beyond our own."

"But you're not suggesting that outsiders should not write about other cultures?"

"No, no. This identification with the other is what a great writer brings to the art of story-making. We should welcome the rendering of our stories by others, because a visitor can sometimes see what the owner of the house has ignored. But they must visit with respect and not be concerned with the colour of skin, or the shape of nose, or the condition of the technology in the house."

It is now my turn to stare out of the window at the six-foot snow drifts and the bare, rickety arms of the trees. The light is beginning to fade and soon I will have to leave. I avert my eyes and turn to face my host.

"Chinua, I think Conrad offends you because he was a disrespectful visitor."

"I am an African. What interests me is what I learn in Conrad about myself. To use me as a symbol may be bright or clever, but if it reduces my humanity by the smallest fraction I don't like it."

"Conrad does present Africans as having 'rudimentary' souls."

Achebe draws himself upright.

"Yes, you will notice that the European traders have 'tainted' souls, Marlow has a 'pure' soul, but I am to accept that mine is 'rudimentary'?" He shakes his head. "Towards the end of the 19th century, there was a very short-lived period of ambivalence about the certainty of this colonising mission, and Heart of Darkness falls into this period. But you cannot compromise my humanity in order that you explore your own ambiguity. I cannot accept that. My humanity is not to be debated, nor is it to be used simply to illustrate European problems."

The realisation hits me with force. I am not an African. Were I an African I suspect I would feel the same way as my host. But I was raised in Europe, and although I have learned to reject the stereotypically reductive images of Africa and Africans, I am undeniably interested in the break-up of a European mind and the health of European civilisation. I feel momentarily ashamed that I might have become caught up with this theme and subsequently overlooked how offensive this novel might be to a man such as Chinua Achebe and to millions of other Africans. Achebe is right; to the African reader the price of Conrad's eloquent denunciation of colonisation is the recycling of racist notions of the "dark" continent and her people. Those of us who are not from Africa may be prepared to pay this price, but this price is far too high for Achebe. However lofty Conrad's mission, he has, in keeping with times past and present, compromised African humanity in order to examine the European psyche. Achebe's response is understandably personal.

"Conrad's presentation of me is my problem and I have a responsibility to deal with it, you understand?" I nod. "I don't come from a 'half-made' society as your 'friend' Naipaul would say. We're not 'half-made' people, we're a very old people. We've seen lots of problems in the past. We've dealt with these problems in Africa, and we're older than the problems. Drought, famine, disease, this is not the first time that we're dealing with these things in Africa."

He takes a deep breath. Beyond him, and through the window, the blanket of night begins to descend over the woods.

"You know," he continues, "I think that to some extent it is how you must feel about your 'friend'. You take it to heart because a man with such talent should not behave in this way. My people, we say one palm nut does not get lost in the fire, for you must know where it is. But if you have 20 you may lose sight of some and they will get burned, but you have others. Well, as you know, we have very few who have the talent and who are in the right place, and to lose even one is a tragedy. We cannot afford to lose such artists. It is sheer cussedness to wilfully turn and walk away from the truth, and for what? Really, for what? I expect a great artist, a man who has explored, a man who is interested in Africa, not to make life more difficult for us. Why do this? Why make our lives more difficult? In this sense Conrad is a disappointment."

© Caryl Phillips