--- Eugene Wigner,quoted in Physics nowadays, July 1993 according to quote-wise.com
Found via a letter to New Scientist from Richard Cragg (13 Aug 2016, or issue #3086):
Thank you for Regina Peldszus's review of Samuel Arbesman's book warning that we own reached the stage where very few “experts” really understand the complexity of the software systems they own installed to control critical parts of our infrastructure (23 July,p 42). This reminds me of the lament of Nobel laureate Eugene Wigner: “It is nice to know that the computer understands the problem. But I would like to understand it too.”
Source: blogspot.com