Traditional historiography of science has constructed secrecy in opposition to openness. In the first part of the paper, I will challenge this opposition. Openness and secrecy are often interlocked, impossible to take apart, and they might even reinforce each other. They should be understood as positive (instead of privative) categories that do not necessarily stand in opposition to each other. In the second part of this paper, I call for a historicization of the concepts of 'openness' and 'secrecy'. Focusing on the early modern period, I briefly introduce three kinds of secrecy that are difficult to analyse with a simple oppositional understanding of openness and secrecy. In particular, I focus on secrecy in relation to esoteric traditions, theatricality and allegory.