American Journal of Mechanical Engineering
ISSN (Print): 2328-4102 ISSN (Online): 2328-4110 Website: Editor-in-chief: Kambiz Ebrahimi, Dr. SRINIVASA VENKATESHAPPA CHIKKOL
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American Journal of Mechanical Engineering. 2020, 8(2), 50-53
DOI: 10.12691/ajme-8-2-1
Open AccessArticle

On the Safety Theorem

Ralph L. Barnett1,

1Mechanical and Aerospace Engineering, Illinois Institute of Technology, Chicago, Illinois

Pub. Date: July 03, 2020

Cite this paper:
Ralph L. Barnett. On the Safety Theorem. American Journal of Mechanical Engineering. 2020; 8(2):50-53. doi: 10.12691/ajme-8-2-1


The contrivances of humankind come into existence through divine intervention, stealth, creative impulse, transformation, systematic design, evolutionary forces, and accidental benevolence. According to the safety theorem the elements of this cosmic stew have a common property, they can all cause harm. The safety theorem appears in many of the most important safety concepts, e.g., the colloquial definition of safety, the technical definition of safety, the control hierarchy, risk abatement, “safety through design” protocol, alternative design theory, and the classification of safety devices. According to the safety theorem, Ÿ The colloquial definition of safety, freedom from the occurrence of injury or loss, exists only as a concept not a reality. Ÿ A safe state does not exist, it may be approached asymptotically in the sense that a cup cannot be emptied by drinking half, followed by drinking half the remainder, etc. You may get as close to empty as you want; but, an infinite number of trials will not empty the cup. Ÿ Laypeople by and large mistakenly believe that products can be made perfectly safe if enough money and time were focused on their design. This paper offers a proof of the safety theorem together with some of its applications.

safety philosophy risk-free inductive inference

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[1]  MIL-STD-882D, “Standard Practice for System Safety,” Department of Defense, 10, February, 2000.
[2]  Lowrance, William W., “Of Acceptable Risk - Science and the Determination of Safety,”1976.
[3]  Barnett, Ralph L., “On the Multiple Definitions of Safety,” American Journal of Mechanical Engineers, June 2020.
[4]  Parker, Earl, “Brittle Behavior of Engineering Structure,” John Wiley & Sons, 1957.