Significant form is a term in aesthetics which refers to the aspect of an artwork (based largely on its structure) which produces an aesthetic response in the viewer. The precise meaning of the term is not obvious, as it depends on a specific theory of aesthetics, and a specific notion of how we respond to art.
A key to understanding the term is the concept of "disinterested contemplation". According to this theory, when one looks at a work of art, for example a sculpture, or listens to a piece of music, one sheds one's ordinary prejudices and emotions and enters a tranquil state where the spectator allows the work of art to weave its spell.
The term 'significant form' was coined by British art critic Clive Bell, the husband of artist Vanessa Bell, in his study of Post Impressionist artists like Paul Cezanne. Clive Bell was interested in the nature of aesthetic experience, in particular the influence of the work's formal qualities on the viewer. He considered that that art affects us by means of its internal qualities: not as a representation of anything in the world, but as an object in itself. The concept of specific form represents the distinct way in which contemplating art will produce a sensation of beauty or the sublime in the viewer. It is an attempt to define that factor which distinguishes a work of art from an image which produces no sensation of beauty.
The notion of significant form perhaps has its most obvious impact when considering music. In enjoying or appreciating a piece of music, we (arguably) do not consider it as a representation of anything else, but as an object in itself. Thus what we perceive is the specific form of the music. (However an alternative view, known as expressionism or emotionalism, holds that music does represent something, i.e. emotions or feelings.)
Specific form also has an application when we consider the visual arts. If we see beauty in an image without responding to what it is a representation of (for example when we contemplate abstract art) we may be said to be responding to the specific form of the image. However, as with most aesthetic theories, the application to other art forms is more complex. When contemplating a poem, are we responding to the meaning of the words, or just their sounds -- or, as one critic has claimed mockingly, simply to the shape the poem makes on the page?
The example of poetry presents one obvious criticism of the idea of the significant form: when we consider how we respond to a poem it is clear that we are always interpreting it, reflecting on the visual images it produces, relating it to our own experiences, etc. Even when contemplating an abstract painting, the colours will stir up memories and perhaps emotional reactions. This means there is no such thing as passive, disinterested contemplation: all engagement with an artwork depends on the viewer's own past experiences, and on how they interact with the work.
Despite these criticisms, significant form can be taken as an attempt to define the nature of beauty. Clive Bell saw the aesthetic response as eliciting similar feelings to religious or spiritual impulses. The concept of significant form gained in prominence in the mid twentieth century with the rise of abstract expressionism, e.g. artists such as Jackson Pollock and Mark Rothko. In orter to understand this new art, critics such as Clement Greenberg sought to reapply the concept.
These later critics' formalist approach carried over into structuralist theory of Roland Barthes and others, but devoid of the sense of beauty or wonder which Bell saw. Ultimately, the concept of significant form founders in critical practice, because it is attempting to characterise our contact with artworks in terms of something beyond words: something spiritual and mystical.