If you have never seriously addressed any of these questions, then your visual and conceptual world will be significantly stretched by the entries for this year's Citibank Private Bank Photography Prize. This is the third year of the award which charts the ever evolving and controversial relationship between photography and art. The success of its two former winners comes as a retrospective slap in the face for protesters like John Ruskin, the 19th-century's first serious opponent of photography as art. In 1997, the panel of judges was seduced by Richard Billingham's starkly unglamorous portrayal of poverty within his own family, while in 1998 they were captured by Andreas Gursky's vision of a soulless, alienated human-race dwarfed by a barren world.
We live in an era which has gone from the naive concept that "the camera never lies," to the cynical and knowing realisation that "photography always manipulates". The five photographers shortlisted for this year invite the viewer to revel in that knowingness - casually mixing visual vocabularies so that references to Hogarth are linked to statements about racism, while a snapshot of a beer'n'kebabs lads' night out echoes photographer Nan Goldin's portrayals of transvestism.
Paul M Smith's photographs are the most disturbing of the selection. In his sequence, (ITALS) Make My Night (ENDITAL) they beckon the onlooker into the riotous carnival atmosphere of male bonding down-the-pub. In one photo a man wears a condom on his head, sticking two fingers up his nose, in another three men piss into a urinal, gesticulating with one finger each at the photographer. These look like the photos of a man who thinks only with his penis - crude, lewd and defiantly snapshot - until you firstly notice that all the faces have been computer-manipulated to be identical, and secondly realise that they are the face of the photographer. Suddenly the photographs take on a new dimension. Still flaunting their laddishness, they can be seen either as a sophisticated comment on the way the individual's identity is subsumed into a group, or as a surreal manifestation of solipsism.
Yinka Shonibare also plays a central role in his own photographs, which first appeared before London viewers in a poster campaign on the underground. (ITALS) Diary of Victorian Dandy (ENDITAL) is a mixture of 19th-century camp and formality, a series of posed photographs depicting a day in the life of a fop at the height of Her Majesty's Empire. The glorious self- consciousness of these photographs in itself subverts the Victorian society they depict, but the most important element is the fact that their central character is black. Their reflection of Hogarth's A Rakes Progress adds to their satirical value, but the satire here operates at a different level - where Hogarth's paintings rely on internal tensions and imagery to convey their message, here much of the irony stems from the outside tension brought by the onlooker's 20th-century re-evaluation of the importance of the black man in our society.
Go on and look into the eyes of any of Rineke Dijkstra's portraits, and you find yourself confronted with a simplicity that simultaneously confounds. Dijkstra is most celebrated for her photographs of gawky adolescents facing the camera from beaches across Europe and North America - and has continued this direct confrontation with awkwardness, photographing young men after they have just emerged blood-smeared from bull-fights or women immediately after they have given birth. Portraiture here isn't presentation of the subject, it is more like an invasion. The tension of the work frequently lies in her subject's simultaneous desire to escape and confront the camera's gaze.
Alex Hartley and Augusto Alves da Silva round off the list of competitors, both playing games with the onlooker's sense of location. Hartley's most famous work Viewer traps a minimalist white gallery inside a giant slide viewer which - are you following this? - itself is displayed inside the gallery. This visual pun on the viewing space inside the viewing space inside the viewing space plays with ghostly lighting effects and dimension - but that's about it. Maybe you have to be there. Maybe not.
Da Silva presents a more interesting situation - a series of photographs of a mountain road taken at intervals of 10 metres. The viewer is surrounded by the road, which is projected from in front and behind. The point of this road is not that it is going anywhere - rather it is the subtle shifts in the scenery which show it to be in a state of Heraclitan flux. You can almost hear the crescendo and the decrescendo of the subjects that breeze in and out of the frames - the rumble of the landrover, the clatter of the horses. Its dreamlike quality and sense of transience is added to by the fact that at the end there is nothing there. Just the mountains and a subtly shifting sky.
The Citibank Photography Prize is at the Photographers' Gallery, 5 and 8 Great Portland St, London WC2, from 6 Feb; the winner will be announced on 9 March