ST AUGUSTINE wrote: "How many common things are trodden underfoot which, if examined carefully, awaken our astonishment?" Augustine clearly did not have Martin Creed's screwed sheet of paper or lump of Blu-Tack stuck to a wall in view when he wrote those words, and Creed would not choose a religious frame of reference for his work; but there is, nevertheless, value in relating Augustine's thought to Creed's work.

Creed revels in the freedom to make art from anything and everything, which was originally granted to artists by Marcel Duchamp, when he attempted in 1917 to exhibita urinal at an exhibition in New York by the Society of Independent Artists. Creed's work retains the playful subversion of expectation and understanding which exemplified Duchamp's original action, and has, as a result, been constantly subject to the same question, which provides the title to this show: "What's the Point of It?"

Through his work, Creed draws attention to the beauty and interest of common things that are regularly trodden underfoot, and he uses the standard gallery techniques of isolating, framing, and exhibiting objects to make us stop and look and examine them carefully in the hope that our sense of astonishment will be awakened. Whether exhibiting an unfolded sheet of paper, stripes of coloured tape, stacks of boxes, or film of various bodily functions, Creed's art transforms everyday materials and actions into surprising meditations on existence, thereby asking us to answer the question "What's the point of it?" In essence, he is saying to us, with Augustine, "Where in all the varied movements of creation is there any work of God which is not wonderful?"

Although the exhibition contains work that is intended to have shock or surprise value (the Sick film or the active but static Ford Focus, for example), the overriding impression of the works included is of wonder. Half the Air in a Given Space, Work No. 200 (the geek in Creed loves lists, sequences, series, and patterns), is a room filled to head height with white balloons. To create the work, the volume of the room was calculated, and the exact number of balloons placed inside to ensure that half of the air within the room was contained within the balloons. When you enter the room to move through the balloons, Creed's rules for the creation of the work simply provide the opportunity for adults to enjoy playing as children do. Unless claustrophobic (in which case, you should not enter), those who plunge in are guaranteed to emerge with a smile on their face.

Equally fun, Work No. 1686 is a Ford Focus car (the most ubiquitous model he could find), which, every few minutes, comes automatically to life - engine starts, horn beeps, doors and bonnet open, wipers start, and the radio plays - without ever moving. Creed has said that "if work is any good, it should be able to live on the street," and this is a work that would have magnified impact in that setting rather than, as here, hidden away on a balcony.

Creed had a Quaker upbringing, which, no doubt, played its partin the quiet minimalism, the simplicity and humility of many of the works included here, such as the understated beauty of installations such as that created from 49 light bulbs (being all the white bulbs made by one company), or a pyramid of stacked toilet rolls. These, then, contrast with the bigger, bolder, brasher works, such as the huge white neon of the word "Mothers", which spins just above head height on a steel girder. Creed has a multitude of tactics and techniques for making us stop and look and look again, making the variety of work in this show as dizzying as the spinning Mothers, Work No. 1092.

What's the point of it? Creed is showing us that art is "anything used as art by people". Creed's work is often immersive and interactive, as with Half the Air in a Given Space, but its implication is more interactive still; life is art - you and I are artists. What's the point of it? Creed's work suggests that there is nothing - even those bodily functions that we normally hide - that is not formed and, by being formed, is wonderful. "How many common things are trodden underfoot which, if examined carefully, awaken our astonishment?"

"What's the Point of It?" is atthe Hayward Gallery, Southbank Centre, Belvedere Road, London SE1, until 27 April. Phone 020 7960 4200. www.southbankcentre.co.uk