Where can I find the definition of "object"?

Question

It has long been my understanding that creatures do not count as "objects", as the rules use that term. I see references to this being the case fairly often, and a lot of rules don't work right without it (for example, if creatures are "objects", then the rule halving energy damage to objects would apply to all energy damage applied anywhere). However, when I went to look up the actual page reference to be able to cite this rule, I was unable to find it. What book establishes that creatures are not "objects", and on what page?

Answer 1

"Object" isn't defined in the core rules

A thorough search for the word "object" in my PDF copy of the Pathfinder core rulebook from 2013 reveals that the term "object" was never given a formal rules definition.

Naturally, it's clear from the core rules that creatures are not considered to be objects.

• No rule defines that creatures are objects. Therefore, there's no rules basis to assume that a creature is an object.
• A brilliant energy sword does not affect undead, constructs, or objects. If creatures were objects, the brilliant energy sword would never affect any creature.
• The rules for Damaging Objects give them immunity to critical hits and nonlethal damage, something which does not apply to creatures.
• The Damaging Objects rules specifies that unattended non-magical items do not make saving throws, with unattended meaning not grasped, touched or worn. If a creature was an object, they would never receive a saving throw unless they held hands with another character, which is absurd.
• Given the logical impossibility of creatures being considered objects, it is highly unlikely that any later Pathfinder rulebook would redefine creatures to be objects. It's also somewhat unlikely that a supplement or adventure module would canonically define object; such a major rule definition would be relevant to the core game, and would appear in errata or FAQ rather than just another sourcebook.