This assumes the environment is completely predictable.
If you know the strength of every link in the chain with perfect accuracy, and you know that the only potential cause of failure is too much weight being placed on the chain, then the only link that can fail is the weakest[1] one because no other failure can happen before that one.
But really you need to design for the idea that various things might happen. Someone else gave the example of a person choosing a link to cut with bolt cutters. The person's choice is what's not predictable in that example.
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[1] And if you assume it's not possible to have two links that are exactly as strong as each other.
If you know the strength of every link in the chain with perfect accuracy, and you know that the only potential cause of failure is too much weight being placed on the chain, then the only link that can fail is the weakest[1] one because no other failure can happen before that one.
But really you need to design for the idea that various things might happen. Someone else gave the example of a person choosing a link to cut with bolt cutters. The person's choice is what's not predictable in that example.
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[1] And if you assume it's not possible to have two links that are exactly as strong as each other.