>At surface level, the adage emphasizes the consistency that arises when information comes from a single source and points out the potential pitfalls of having too much conflicting information. <i>However, the underlying message is to question the apparent certainty of anyone who only has one source of information. The man with one watch has no way to identify error or uncertainty.</i><p>This ambiguity between endorsing one or two is why I kind of prefer the version of this law Fred Brooks cited:<p>>An ancient adage warns, "Never go to sea with two chronometers; take one or three." The same thing clearly applies to prose and formal definitions. If one has both, one must be the standard, and the other must be a derivative description, clearly labeled as such. Either can be the primary standard. Algol 68 has a formal definition as standard and a prose definition as descriptive. PL/I has the prose as standard and the formal description as derivative. System/360 also has prose as standard with a derived formal description.<p>In this context, the reader can be much more trusted to see that one chrono beats out two only by being cheaper (which might be worth it for short voyages), and one description beats out two only by being unambiguously the standard (which might be worth it for small or exploratory projects).
<i>List of chronometers on HMS Beagle</i> <a href="https://en.wikipedia.org/wiki/List_of_chronometers_on_HMS_Beagle" rel="nofollow">https://en.wikipedia.org/wiki/List_of_chronometers_on_HMS_Be...</a><p><pre><code> Larcum Kendall's K1, a copy of John Harrison's H4,
H4 had cost over £20,000 (inflation adjusted £3,260,000) to develop. Kendall's K1 cost £500 (now £74,000) and his cheap model, K3, cost £100 (now £13,400), but by the time the Beagle voyages were over the cost of a good chronometer had fallen to under £40 (now £4,200).
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Marine clocks were serious business.
I was once told by an older and wiser scientist that you should never measure the same phenomenon with two instruments. If you do, your entire study turns into an inter-instrument comparison.
“Certainty breeds insanity”, or “make a pledge and mischief is nigh”, are two translations of one of the three things inscribed at Delphi.<p>The other two:<p>- “Know thyself.”<p>- “Everything in moderation.”<p>Good advice, difficult to keep in mind!<p><a href="https://en.wikipedia.org/wiki/Delphi" rel="nofollow">https://en.wikipedia.org/wiki/Delphi</a>
"A person with a watch knows what time it is. A person with two watches is never sure."<p>Not quite. A more accurate version would be:<p>"A person with a watch thinks they know what time it is, but they are wrong. A person with two watches is never sure, and they are right."<p>---<p>EDIT: And Einstein is watching from above, smiling.