With two and half millennia of philosophical ponderings since Plato and Aristotle, several hundred years of modern science, and perhaps one hundred and fifty years of near modern engineering – surely we know sufficient about the physical for ordinary product design?

While this may be true of the physical properties themselves, it is not the fact for the way people interact with and rely on those properties. It is only when the nature of physicality is perturbed by the unusual and, in particular the digital, that it becomes clear what is and is not central to our understanding of the world.

Increasingly, digital aspects of physical products mean that causal effects are created programmatically rather than mechanically. Sometimes this is because the effect is intrinsically digital or electronic (e.g. TV remote), sometimes because this is cheaper, or more reliable than physical controls (e.g. washing machine control panel), and sometimes because of the increased flexibility of power gained (e.g. central heating control allowing arbitrary complex heating programs).

Whichever is the reason for the design choice, the user is faced with objects that are partly physical – hold it, touch it, push it, and partly digital – things happen. Even hidden physical mechanisms can be confusing and this is typically more so when the linkage between cause and effect is electronic. Whilst the term ‘virtual reality’ is usually taken to mean physical-like worlds created within a digital environment, arguably (in a different sense) ‘virtual reality’ will be the norm for 21st century life in that our day-to-day interactions with the physical world become digitally mediated.