  Of course, the metaphor of economy is also used in economics. According to Mach’s own recollections of his intellectual development in a 1910 essay, “The Guiding Principles of My Scientific Theory,” he first understood science as ‘okonomisch’ in 1864, through discussions with his friend E. Hermann, a political economist. In the same passage, Mach proceeds to note that he was well prepared for this idea through his biological background, and in fact the two combined to form what became his ‘biological-economical theory of knowledge’. [Mach 1910: 30–31]