In Built upon Love Alberto Perez-Gomez linked together three concepts that can be said to be essential in any architectural work: project, program and promise. In architecture an analogous relationship exists between the needs of the work and the resources of the world, played out at the building's borders, through elements that enclose and open the interiors, constructed of course, and defined geometrically. Aristotle was concerned with tragic drama, but the etymological ties between the words plot, plat, and plan suggest there is no mistake in applying his principle to architecture too. Once architecture's essential poverty is observed, elements such as apertures become instruments of longing. As if Rainer Maria Rilke was writing about concepts of connection and communication that are common in architecture, Rilke argued that "merging" is in fact senseless; when approximated it results in a "hemming in", a denial of freedom.