Zen and the Art of Template Engines

Without exception, programmers espouse separation of logic and display as an ideal principle. In practice, however, programmers and template engine producers are loath to enforce separation, fearing loss of power resulting in a crucial page that they cannot generate while satisfying the principle. Instead, they encourage rather than enforce the principle, leaving themselves a gaping "backdoor" to avoid insufficient page generation power. Unfortunately, under deadline pressure, programmers will use this backdoor routinely as an expedient if it is available to them, thus, entangling logic and display.
- From Enforcing Model-View Separation in Template Engines

Koan: The problem is not how to separate logic and display. It is how best to capture this entanglement.