sit looks like. is there that is a chair that That 'Chair' refers to a Class. Chair is subclass of 'Physical Object' which under particular definition simply Set Particles. Now as Class we must understand what its Instances are. Well they're certainly Physical Objects. But else they possess? See.. that's difficult define. One may separate the requirements for Object be into two components: function and form. Function something able do. Notably Human can on it. Form Here it gets bit ambiguous because really depends your personal definitions. However I will posit class adds both function Now note not all subclasses behave this way. A 'Rod' defined purely by form 'Switch' function. Thus if satisfies has. Ahh but now reach question: same Chair? Is Object? How does one refer single it's underlying set Particles different? say same? change our definition bit. We define dynamic Particles in sense any at point time. Here use cognition-oriented i.e doesn't try explain actually rather just explains things way humans understand. when (something specific particles each time). soon cease chair. Why? per Object next moment time could completely unrelated like AC unit over there or even selection from various galaxies. But remain Chair. meant