Criteria of a practical truth (of a principle, a rule, etc.)

1. It works
2. It's working leads you to the end you actually want. E. g. if someone doesn't think reading is important, "How to read s book" has little practical truth to them, regardless of its soundness.

Agreement with a practical book means your understanding of what it is right to aim for and how accords with the description in the book.

If something you believe is practically true in this view, Practice what you believe is true.

Related:

• Criticise the book rationally
• Bottom-up design is more robust than top-down
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References

‣ (Mortimer J. Adler)