A method of shape generation using shape grammars which take shape as primitive and have shape-specific rules is pre- sented. A formalism for the complete, generative specifica- tion of a class of non-representational, geometric paintings or sculptures is defined which has shape grammars as its structural component. Paintings are material representations of two-dimensional shapes generated by shape grammars, sculptures of three-dimensional shapes. Implications for aesthetics and design theory in the visual arts are discussed. Aesthetics is considered in terms of specificational simplicity and visual complexity. In design based on generative specifications, the artist chooses structural and material relationships and then determines algorithmically the resulting works of art.