 It is because of the imaginary quantities in quantum mechanics (where the commutation rule for canonically conjugate variable, p and q, introduces Planck’s constant into the formalism by qp − pq = ih/2π that quantum mechanics does not give us a ‘pictorial’ representation of the world. Neither does the theory of relativity, Bohr argued, provide us with a literal representation, since the velocity of light is introduced with a factor of i in the definition of the fourth coordinate in a four-dimensional manifold (CC, p. 86 and p. 105). Instead these theories can only be used symbolically to predict observations under well-defined conditions. Therefore, many philosophers have interpreted Bohr as an antirealist or an instrumentalist when it comes to theories. However, Bohr’s reference to the use of imaginary number in quantum mechanics as an argument for his rejection of a pictoral representation may seem misplaced. The use of imaginary numbers is more a question about the conventional choice of scale whether measurements should be represented in terms of imaginary or real number than an indication of a certain magnitude expressed in terms of these numbers is not real. Dieks (2017) gives a nuanced discussion of Bohr’s argument, and he concludes that in the context of quantrum mechanics Bohr saw imaginary numbers to be associated with incompatible physical quantities. 