This thesis concerns the ability of individuals to engage in transformative use of copyright expression without the permission of the copyright owner. Transformative use refers to the use of existing expression as an input into the creative process, resulting in the creation of new expression that, while still embodying elements of the original work, is original in its own right. This type of creativity is beneficial for society and should be encouraged. Individuals should have the ability to express themselves, and participate in the interpretation of their culture. My enquiry has shown that Australian law does not facilitate transformative use. Many forms of transformative expression are not currently permissible without the express permission of the copyright owner. Copyright theory, however, is not in accordance with such a prohibition on transformative use. I will suggest some legislative and judicial reforms to Australian copyright law that can have the effect of encouraging transformative expression, while at the same time providing an economic incentive to invest in creative expression and protecting the legitimate interests of creators in their works. The primary modification I suggest is that the definition of 'substantial part' in the Coypright Act 1968 (Cth) should be read, in accordance with the interests served by copyright, to allow a consideration of the context in which copyright material is taken. The seeds of such an approach are present in modern judicial interpretations; the discussion that follows attempts to show how such an approach accords with copyright theory, and why it should be preferred by the judiciary. Firstly, with respect to the economic rights, transformative uses of copyright material which are not substitutable for the original expression should not be found to reproduce a substantial part of the original. Secondly, questions of substantiality in the moral rights should be interpreted to protect authors from unreasonable commodification of their works. To the extent to which it is unclear how the right of integrity applies to the context in which a work is used, as opposed to the modification of the work itself, I submit that it should be interpreted such that authors have a right to object to the commercial association of their work with a position, product, or service against their will. Alternatively, I submit that legislative reform to include an open ended defence to copyright infringement could provide much needed flexibility in the Australian system. Such a defence could draw primarily on the US 'fair use' defence, but certain limitations of the US defence could be overcome in an Australian context. Again, as the theory shows, the primary consideration for infringement of the economic rights in transformative uses should be the degree to which the transformative use is substitutable for the original. Finally, I submit that the reasonableness defence to infringement of the moral right of integrity should be read in such a way as to ensure that the personal interests of authors does not interfere with the legitimate self-expression of future authors. I will show that the theory does not support moral rights to the exclusion of either the ability of future authors to self-actualise. The operation of the reasonableness defence should be clarified to ensure that the legitimate interests of both past and future creators are recognised.