but one whose only audience is fellow performers.
The above quote according to Hymen Bass in Mathematics and Teaching (2015) is due to Samuel Eilenberg.
The next quote, due to Bass himself, is on the approach taken by some mathematics educators to counter the “content only” type of teaching.
This approach poposes offering tangible and somehow “real-world” related mathematical activities with which to engage learners but leaving the development of mathematical ideas to largely unrestrained student imagination and invention. In such cases, the discipline of mathematical ideas may be softened to the point of dissipation.