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For All Practical Purposes (FAPP) is a pragmatic approach towards the problem of incompleteness of every scientific theory and the usage of asymptotical approximations.
Usually, when a physicist makes an approximation - which can't be justified on rigorous grounds - he tends to justify it by saying that the results obtained are good for all practical purposes (FAPP), meaning that they agree with our experience and approximation errors cannot be detected in practical measurements (for instance, if the error is smaller than the measurement resolution).
FAPP theories are incomplete or lackly-based theories that nevertheless have very high agreement with experiments and tend to be very useful for all practical purposes.
Famous quotes containing the words practical and/or purposes:
“Philosophy, certainly, is some account of truths the fragments and very insignificant parts of which man will practice in this workshop; truths infinite and in harmony with infinity, in respect to which the very objects and ends of the so-called practical philosopher will be mere propositions, like the rest.”
—Henry David Thoreau (1817–1862)
“What happened at Hiroshima was not only that a scientific breakthrough ... had occurred and that a great part of the population of a city had been burned to death, but that the problem of the relation of the triumphs of modern science to the human purposes of man had been explicitly defined.”
—Archibald MacLeish (1892–1982)