An ongoing debate in doctoral research in art and design is whether the submission of a thesis should be a necessary requirement, or whether it should be possible to submit practice work only for the degree. In order to illuminate this matter, it seems necessary to examine the role of the artefact in relation to the nature of theory and practice and the requirements of (doctoral) research to produce explicit and communicable knowledge. To begin with, I review a paper by Biggs (2002) about "The rôle of the artefact in art and design research" in which he argues that the interpretation of artefacts is affected by their context, and that therefore artefacts need to be explicated through contextualisation if they are to communicate knowledge. This leads me to question firstly the relationship between the artefact and its contextualisation/explication, and secondly how artefacts can be used as knowledge base in research. As a basis for the discussion, I adopt Fawcett's (1999) understanding that the knowledge contribution of research is made in the form of theory. For research in art and design using practice this means, while the task of the research is to generate knowledge, i.e. to make the nature of things, processes, relationships etc. explicit in form of theory, the practice itself can serve to provide data and evidence. I use two quotes from Cummings (1993) to further problematise the relationship between practice and theory, and artefact and text within research. I use this discussion to demonstrate that artefacts/creative practice may be understood as a phenomenon or substance that provides a basis for theory generation and that in turn is illuminated by this theory. The discussion further illustrates that the need to explain objects arises because of their complexity. Objects have multiple levels of reality, e.g. material, visual, functional, symbolic etc. Artefacts therefore are open to interpretation. Using problem analysis supported by object examples from my own thesis, I conclude this study with a discussion of the conditions under which artefacts can provide unambiguous evidence and thus some kind of reliable knowledge. I explore some of the multiple levels of object-reality and I show under which conditions we can determine one specific level. The discussion reveals a number of ways how objects can be employed as source for knowledge creation. Thus I show that artefacts can be used as:"Quest", i.e. the object can cause me in the first place to search for explanation – thus initialising research;Evidence of the making process; both in technical as well as conceptual terms;Evidence in terms of the characteristics of the object itself;Evidence in terms of social and cultural phenomena.