Commonly, the central question of curriculum study is posed simply as "what knowledge is of most worth." The question, of course, is deceivingly simple, and many curriculum scholars have complicated the question by asking such things like: most worth for whom; for what purpose; and in what context? The four articles in this issue of Curriculum Inquiry (CI) show different ways in which curriculum scholars complicate the question of knowledge, by taking the question further to examine: how precisely do we use evidenceand more specifically come to "see" evidenceto confirm that we know what we think we know (Baker); under what conditions can certain knowledgesparticularly youth knowledge in school contextsemerge and be known (Rubin, Ayala, and Zaal); how do researchers make sense of the political discourses, such as neoliberalism, that shape knowledge (Schmeichel, Sharma, and Pittard); and how teachers are constructed as experts within the structural power relations that define which knowledge is deemed most worthy (Theodorou, Philippou, and Kontovourki). Each of the four articles offers a different window and sheds a different light on questions of knowledge, knowledge production, knowledge mobilization, and what counts as evidence. Taking up the question of evidence, curriculum theorist and historian Bernadette Baker traces the intertwining of discourses of vision and what comes to be seen as evidence. In her wide-ranging article, "To Show is to Know? The Conceptualization of Evidence and Discourses of Vision in Social Science and Education Research", Baker traces how visuality became the dominant mode for constructing and collecting empirical evidence. Through a close reading of historical and philosophical texts, Baker traces the emergence of "visuality" through debates about what counts as empirical evidence. She argues that the arbitrary link between what is seen and what is known, manifested in the maxim "to show is to know," restricts the modes of argumentation through which knowledge claims are made as well as what and how phenomena becomes evident. Baker applies her analysis of the historical link between visuality and empiricism to current research and debates around the notion of "big data" and the recent interest in mindfulness practices among educators and psychologists. The two examples are intriguing, as they "appear to represent oppositional possibilities for procedural reason in education" (p. 166), that is, they seem to require different modes of knowing. Yet, Baker argues that how knowledge claims are construed within these areas of investigation "invite a series of new questions around the role and nature of evidence and vision and this is particularly so in current efforts to "soften" big data as it is taken up in education and to "harden"