Interactivity, at its core, whether in a device, program, gadget, tool, or anything else, is the capacity to accept an input and convert it to some variety of output. There is an inherent, reciprocal relationship between the impetus and the result, although not necessarily a distinct logic. “Well-designed” interaction typically observes some logical paradigm or metaphor, something that associates an end result with a corresponding input, but any scenario that asks for A and produces B is fundamentally interactive.

Physical interaction, by definition, observes the same rules as general interactivity, but what differentiates physical interaction is something of a semantic debate. In my mind, physical interaction is defined by a physical impetus, rather than a physical output. Admittedly, there isn’t a great deal of examples of non-physical interaction that produce a physical output, but to discus semantic meaning is to indulge in edge cases, so bear with me. The meaning of physical input is itself subject to debate. Obviously, buttons, finger taps and the like are physical, but what about voice controls? I argue yes, since sound is ultimately a physical medium, but what about a neurological interface? Again, probably yes, but I’m also not wholly comfortable with a reality where my phone can read my mind, so I’d rather not go down that road.

As previously mentioned, a “well-designed” interface behaves according to some coherent logic, although the origin of that logic isn’t necessarily inherently logical. This is particularly true among digital interfaces, where common practice (or misguided design goals) lead to designers implementing skeuomorphic metaphors derived from analog counterparts that don’t necessarily correspond to any intuitive logic in a digital realm outside of assumed familiarity with the source material.

In a world where nearly everything offers some fundamental utility, what makes something non-interactive? At this point, I’m no longer sure. Watching a movie is a passive experience, but the means and tools we use to watch are interactive. Books, while seemingly passive objects, require active engagement both for interpreting meaning and articulating the physical turning of pages. Probably the most characteristic attribute of a non-interactive object is stasis, particularly as we relate to the object. The question though, is what do we experience today that is truly static, and the answer is, I don’t think I know anymore.