The solid work of a self-conscious conclusion requires great perseverance and caution. As a rule, it is very slow and is rarely helped by a flash of insight. There is little in it of the readiness with which historians or philologists sort through the most diverse experiences in their memory. On the contrary, it is an essential condition for methodical progress in thought that a thought remained concentrated on one point, undisturbed by other questions, undisturbed from wishes and hopes, moving forward only according to its own will and its conclusions. A famous logician, Stuart Mill, explained his conviction that, in recent times, the inductive sciences have done more to advance logic's methods than have all academic philosophers. An essential reason for this is that in no other field does an error of thought lead so easily to false results as it does in those sciences where the outcome of a thought process can be directly compared with reality.
[ . . . ]
Source: „Ueber das Verhältniss der Naturwissenschaften zur Gesammtheit der Wissenschaft," in Vortäge und Reden von Hermann von Helmholtz [“On the Relationship of the Natural Sciences to the Whole of Science,” in Lectures and Speeches by Hermann von Helmholtz], 2 vols. Fourth edition. Braunschweig: Friedrich Vieweg und Sohn, 1896, vol. 1, pp. 159-65, 172-73, 175-78.
Translation: Jonathan Skolnik