Murphy's Corollary: anything that did not go wrong could not have gone wrong

The law as we quote it #

The statement of Murphy's Law that has gone into the popular lexicon is Anything that can go wrong will go wrong. That's probably not what Murphy said, but that's how we quote him today. And when we quote Murphy in this way, it is likely that we are doing it mostly for comic or ironic effect.

Because to be clear, nobody really believes this statement of Murphy's Law. Almost anything could go wrong, and if it were really true that anything that could go wrong would go wrong, then most everything would go wrong. And most things don't.

Where it came from: the rocket sled #

The law is generally attributed to Capt. Edward A. Murphy, a development engineer from the Wright Field Aircraft Lab working on Air Force Project MX981 at Edwards Air Force Base in 1949. The rocket sled tests were designed to see how much sudden deceleration a person could withstand in a crash.

Murphy had brought a g-force sensor made of a bridge of four strain gauges. The gauges could be wired together in more than one way, and one of those ways would cancel them out and produce a zero reading. After just such a result, Murphy allegedly remarked in frustration, If there is any way to do it wrong, he will, referring to the technician who had wired the gauges.

The basic observation can be found at least 70 years before Murphy's statement, and likely goes back much further, but today it is almost universally attributed to him.

What Murphy was really saying #

The statement is obviously false, but only because the common phrasing omits one important word. What the law should say is: anything that can go wrong will go wrong, eventually. Given enough trials, if something can go wrong, it eventually will.

The value of Murphy's observation is not in its pessimism but in the way it informs design, both the design of things and the design of procedures. If we can design out the possibility of doing it wrong, we should. The polarized electrical plug is one example.

A tragic illustration was the series of F-86 crashes in which a bolt on the aileron cylinder was installed upside down, locking the ailerons under certain loads. The incorrect installations were reportedly traced to one older worker on the assembly line, who ignored the instructions because he felt he knew better how the bolt should go.

The corollary #

But if Murphy's Law were true, if anything that could go wrong really would go wrong, then a corollary would also be true:

Anything that did not go wrong could not have gone wrong.

Even though we don't believe Murphy's Law, we are surprisingly subject to being seduced by this corollary. If nothing did go wrong, then nothing could have gone wrong. We take a positive outcome as evidence that a positive outcome was inevitable.

That is what happened with our decision to use top landings to save time in production test flying. We had a long string of successes, and each one reinforced our perception that success was an outcome we could rely on. The problem with that perception is that our data set is too small, at least at the beginning of any such process.

Warning signs, suppressed #

We had many indications during those fifteen years of successful landings that the technique was of questionable safety. There was always some turbulence, rotor or convective or both, as we passed through twenty to fifty feet above the ground. Hang gliders lose control authority progressively at low speed, so we approached fast, passed through the turbulence, then entered a wind gradient where airspeed dropped dramatically as we rounded out to follow the slope, and flared almost at once.

Many times, passing through the turbulence and into the gradient, I remember thinking, this may not end well. And yet, with each successful landing, my next thought was, well, that was fine, no problem; what could go wrong?

I had even seen other pilots have significant crash landings, sometimes damaging gliders, and I rationalized those as poor technique. It was only when it happened to me, after what I judged a perfectly executed approach, that I realized my doubts had been correct, and that suppressing them had been Murphy's Corollary in action.

@misc{meier2026corollary,
  author = {Meier, Mike},
  title  = {Murphy's Corollary: Anything That Did Not Go Wrong
            Could Not Have Gone Wrong},
  year   = {2026},
  url    = {https://meiersafe.com/murphys-corollary/}
}