Olszewski claims that the Church-Turing thesis can be used in an argument against platonism in philosophy of mathematics. The key step of his argument employs an example of a supposedly effectively computable but not Turing-computable function. I argue that the process he describes is not an effective computation, and that the argument relies on the illegitimate conflation of effective computability with there being a way to find out.

%B Philosophia Mathematica %V 19 %P 74–89 %G eng %R http://dx.doi.org/10.1093/philmat/nkr001