Mediating humanity's degree of linkage to nature has been one of architecture's long time roles, one that intensified over the 20th century as it became increasingly difficult to deny the concrete effects man has on the natural world. This created a new baseline for contemporary architectural debate, one focused on human responsibility for nature's processes. This paper will show that using human responsibility as a baseline for architecture may reinforce and recycle a retrograde framework for human agency which is often (though at times productively) little more than a fiction. To this end I cut across three episodes, each exploring--with a pair of examples, one historical, one contemporary--architecture's tenuous relationship with mold, (the fungus,) a figure present architecture across the historical record. Ubiquitous, contentious and diverse, mold suggests that nature be seen in an array of contiguous terms--good, bad, ugly and beautiful. This disruption of the expected intersections of man and nature highlights the direct effect our conception of nature has on the tectonic, interpretive and experiential possibilities of architecture.