Final answer:
The quotation emphasizes the need to critically test treatments with uncertain effectiveness instead of relying solely on custom or wishful thinking. This ensures evidence-based medical practices and avoids potential harm to patients.
Step-by-step explanation:
The quotation is highlighting the importance of critically testing treatments, both old and new, whose effectiveness is uncertain. It suggests that in such cases, there is a greater moral obligation to subject the treatments to critical examination rather than continue prescribing them based on custom or wishful thinking alone.
By subjecting treatments to critical testing, it allows for a thorough evaluation of their value and effectiveness. This ensures that medical practices are evidence-based and avoid potential harm to patients.
An example of this could be the evaluation of alternative or complementary therapies that may lack scientific evidence but are still widely used based on tradition or anecdotal evidence.