"Knowledge and error flow from the same mental sources; only success can tell the one from the other."

Ernst Mach's statement from 1905 continues to resonate in Safety Science: It's referenced by scholars like Jens Rasmussen, Karl Weick, James Reason and Erik Hollnagel. It’s always (?) referenced in the above 1976 English translation.
 
Jens Rasmussen, in his “Trends in human reliability analysis” (1985) used Mach’s statement to illustrate that errors are integral parts of learning mechanisms.

James Reason, in his book "Human Error" (1990), draws on Mach's insights to highlight that errors stem from normal cognitive processes.

Erik Hollnagel further extends Mach's influence in his books 'FRAM' and 'The Efficiency-Thoroughness Trade-Off' (ETTO). He uses Mach’s statement to describe that individuals often make trade-offs favoring efficiency over strict adherence to rules, influencing outcomes. So, in organizational dynamics, the pursuit of productivity sometimes contradicts stated “safety first” policies.
In the FRAM book, Mach's work serves as a foundation for the argument that accidents are not solely a result of intentional deviations or misconduct but are inherent in the nature of activities. Absolute safety is unattainable, and focusing on daily practices and understanding systemic functioning becomes more valuable than criminalizing accidents.

Skilled professionals can make critical errors with potentially fatal consequences due to the nature of cognitive processes, but, the same cognitive processes help them to inconspicuously do their normal work, or, to save the day.
 
But what exactly did Mach write besides this famous quote? The original German text from 1905 shows that he explores the interdependence of adaptation, perception, and behavior in living organisms. He goes into the complexity of consciousness. He writes about the potential for errors in perception, and cautions against the impact of expectations and imagination on observations.
 
Mach defines a correct judgment (“an insight”) as one that aligns appropriately with physical or mental conditions, resulting in biologically beneficial experiences. Conversely, judgments that prove incorrect are labeled as errors, and intentional misleading judgments are categorized as lies. The same mental processes leading to recognition can also result in errors, influenced by factors like sensory observation and conceptual thinking. So, precise observation and analysis of terms is needed to avoid errors.

“Erkenntnis und Irrtum fließen aus denselben psychischen Quellen; nur der Erfolg vermag beide zu scheiden. Der klar erkannte Irrtum ist als Korrektur ebenso erkenntnisfördernd wie die positive Erkenntnis.”

Mach, E. (1905), Erkenntnis und Irrtum – Skizzen zur Psychologie der Forschung, Leipzig: Johann Ambrosius Barth.