This paper gives an overview of the way foresight knowledge concerning scientific and technological developments is deliberated in policy. It also offers an approach to assessing the quality of foresight knowledge generated during foresight exercises. Although “foresight knowledge” is a special case, the idea of having a procedure, approach or method available for assessing the quality of knowledge is tempting: foresight knowledge comes from various sources such as different scientific disciplines, normative visions on the future, planning, and scenario’s. It also receives input from different sectors of society, such as industry, academia and civil society. How can we then assess the quality of knowledge inputs from such diverse sources and its implication for foresight exercises? This paper is a first attempt to address this subject matter. We realise that this type of work has not been done before, and we hope therefore that this first attempt will stimulate others to further explore this issue. Since the aim of this paper is to address “knowledge assessment” on “Foresight knowledge”, we will first give an overview of what foresight actually is, before entering into the core issue of the paper – that is, what “knowledge assessment” addresses and where it could intervene in the framework of a Foresight-exercise. It may thereby also clarify the relevance of knowledge assessment beyond the context of foresight knowledge itself; although it will be seen that “foresight” is a particular case for which “knowledge assessment” is required. The first part of the paper is devoted to the deliberation process in the policy context and especially identifies the normative dimensions of such a process and its consequences for knowledge generation. The second part will enter into the issue of knowledge assessment of foresight knowledge. In both parts foresight knowledge is illustrated by reference to issues of sustainable development.