The conceptual artist picks up a hammer in place of a paintbrush, at which point the wooden picture frame is split and splayed by a violent blow. The fine threads of frayed firewood are then gathered, set alight and used to toast marshmallows without there necessarily being any intention of eating them. As far as conceptual art holds itself hostage to this metaphor, these marshmallows are merely marshmallows of the mind.

An intellectual idea is at the heart of this artistic experience, and its inquiry is more important than the framed and finished product. This self-conscious snubbing of the aesthetic follows in the footsteps of Marcel Duchamp with his prototypical readymades, including the practical joke that sparked an artistic revolution. Fountain (1917) is a urinal-basin signed under the pseudonym ‘R. Mutt’ and submitted for inclusion at a New York gallery exhibition, which was rejected with rage before its eventual showcase. Whilst this sculpture may seem to simply be a bog-standard sanitary item mass-produced by machines, it succeeded in shifting the focus of art from material craft to intellectual interpretation in one swift and shocking swoop.

A step further would be to say that it does not matter if a conceptual artwork has been made at all, and that its conceptual essence can be adequately captured in a description. If this is the case, we then find ourselves trudging through an abstract realm as treacherous as quicksand. If I claim to bury a broken heart beneath a floorboard in the corner of the room it once loved in, performing this under the pretext of a poetic-philosophical investigation into the concept of cracks, and then concluding that all cracks are either chasing each other or chasing themselves, am I a conceptual artist?

I have also been wondering whether a shadow can be copyrighted, whether it belongs to the object which casts it, to the space in between, to the source of light or to the eyes that perceive it. As pointed out by a lawyer friend, this musing is built on the shaky structures of a significant oversight. Since a shadow is debt, that is to say the lack of light, it is owed rather than owned. The fact of the matter is that translating from the mental to the material realm is essential if transforming philosophy into a piece of art. It can be difficult to draw the line between what is conceptual art and what is not, because such categorisation can be so easily confused with intention. However, since conceptual art is linked to our conception of art, perhaps challenging this difficulty is the point.

The claim that a conceptual artwork doesn't necessarily have to exist is further undermined by Sophie Calle, considered to be the leading conceptual artist of France. She is a controversial figure known for invading privacy in the name of art, and her concepts shatter into shards of syllables when you try to write them down; leaping over the lines of the page, these pieces of art then slip into their slippers and run away. In stealing snatches of strangers' existences, secretly following their steps and taking their photographs through Paris, once all the way to Venice as in Suite Venitienne (1979), she is celebrated for the audacity of actually having done so.

Her most audacious act was not whilst working as a chambermaid, taking pictures of the guests' messy rooms and examining the contents of their cases for a project entitled The Hotel (1981). Rather, it was after stumbling across an address book in the street. She photocopied it, sent the original back to its owner, and then set about calling the numbers and asking questions to paint a conceptual portrait of the stranger. The transcripts of these conversations were published under the title of The Address Book (1983) and featured alongside photographs of people engaged in the man's favourite activities. Whilst some people might compare her to the wicked witch of The Wizard of Oz, cruelly spying on the innocent through her conceptual crystal ball, there is still cause for celebration. She has guts: an artist who slaps you on the shoulder rather than politely shaking your hand. In short, the power of a conceptual artist doesn't just lie in conceptual prowess, but in being so bold as to transform it into reality.