The Primacy of Practice in Nicholas Lash
The truth of christian ‘theory’ is too closely bound up with the quality of christian ‘practice’ for it to be possible to press the necessary distinction between ‘theory’ and ‘practice’ to the point where they can be handled as fundamentally separate issues. In 1837 Newman claimed that ‘Action is the criterion of true faith.’ His principle that ‘The safeguard of Faith is a right state of heart’ applies, not only to the individual, but to the church as a whole. In order to assess the ‘truth,’ or faithfulness of a particular development of christian doctrine, it will be insufficient to ascertain that the development is a theoretically justifiable interpretation or application of new testament teaching. It will also be necessary to ask whether the development in question expresses or embodies a style of life, an ethical response, which is in conformity with the style of life commanded or recommended by the gospel.
from Change in Focus, (Sheed&Ward, 1973), 102-3.