Say we have what we would call an 'object' made of many components, can these 'components' be named objects themselves? In the case do we have an object or many 'objects'? Do we define an object to be 'isolated' things? Is it a choice how we express whether we have one or many 'objects' if they form a greater whole? Or is it more of a linguistic thing? Such as the idea of the question that 'is a Rubiks cube on cube or many cubes (attached together), which we could argue is more of a 'linguistic' issue?
It's a pragmatic thing more than a linguistic thing.
- If you want to go to the store, you think about your car
- If your car won't drive, you think about what part of it is at fault: engine, transmission, wheels, etc
- If you're trying to fix one of those parts, you think about its parts (the wheel's hub, tire, or axle; the engine's pistons or cranks; the transmission's gears or clutch...)
If you're merely driving around there's no sense thinking about all the various parts and mechanisms of the car. It's a car, and that's the only thing you need to know. We pick the level of analysis we need for the pragmatic task at hand, and that determines which things we constitute as undivided objects.
Disclaimer: concepts from my last book, I do Systems research. This is related to the Systems Theory.
- The object is the counterpart of the subject, being both the members of an interaction. An interaction implies a relationship between two systems, which is a bit long and complex to describe here. Object and subject are just two archetypes of systems. There is no object without subject and vice-versa.
"The rock is heavy" implies an interaction between a subject (the observer) and an object (the rock). Language always imply in a sentence that the subject is the observer. The imperative sentence "Sleep!" is an equivalent of "I-subject ask/command you-object to sleep". The sentence "That's a nice bike" is equivalent to "That bike-object is nice for me-subject". The sentence "one plus one is two" means "I-subject recognize the object-[one-plus-one is equal to two]", etc.
Absolutely all systems are ideals. Therefore, the object is always an ideal, a rational construct. For example, the moon is something we can't touch, explore. We just have the subjective ideal of the moon in our heads. Take a rock, and the situation is similar. A rainbow is the same.
The universe is constant change, there is literally nothing, absolutely nothing, radically nothing that is static. Everything changes. But our mind makes it appear as static. You change every second, the person you are looking in the mirror is not the same that was one second ago, the river is never the same.
Now, this is really amazing: not only our mind makes us perceive objects as static, but also our bodies. We are tuned to perceive the phenomena we perceive.
Thermodynamics differenciates such perspectives, the changing reality, and the apparent staticity as "microscopic" and "macroscopic".
- Now the answer to your question becomes evident: the boundaries of objects (or things, when we refer to its physical façade), are macroscopic: defined subjectively by our mind and by our body. A rainbow has no other boundaries than those that our body and our mind grant to it.
Consider the case of a truck of apples in multiple states: immature, mature, rotten, broken, of different varieties, etc. It is literally impossible for two persons to count the same number of apples. And if both enter into a very detailed and strict definition of what is an apple, the definition is still subjective for those two persons. Any person will count a different number.
The subjectivity of our mind to define the boundaries of an object (e.g. Where does a tree starts and where does it ends) is easy to grasp. But not the physical subjectivity, the subjectivity of our body. Just think that aliens might be made with different physical structures and their hands can pass through walls. In such case, their perception of mineral-objects would be completely different, they would evidently unable to define boundaries on everything mineral on earth.
I think it’s largely a linguistic thing, since the object/objects is/are what they are however we describe them. A more intriguing question (for me anyway) is that if you dismantle a Rubik cube into its component parts, where did the cube go. I digress. The idea of an object is typically thought of as a physical manifestation of a recognisable concept such as a chair and it’s entirely valid that this could be made of other objects and/or a part of a greater object. If you have a different definition of what constitutes an object then the answer may be different.
It depends on your metaphysical presuppositions. Philosophers have wildly different ideas on how to determine what a thing is. Pragmatically, one can resort to picking something up and seeing if it falls apart. Rationally, one can draw the conclusion, as in mereological nihilism (SEP) that macro objects don't exist at all, but there's merely object-like configurations of things. Sometimes it doesn't even require fancy logic. We all have noses, right? Where does the nose end and the cheekbone begin? To some extent, what a nose is somewhat arbitrary, and different language communities might have different definitions.
Spatiotemporal Boundaries and Identity
Your question is intimately linked to ontology, because it asks after the structure of things that exist. In Western philosophy, there's is a bias to seeing 'objects' as static things with clear cut boundaries and definitions. A baseball is not a basketball and that's because both satisfy certain criteria of sufficiency and necessity. Science often provides elaborate procedures to define and measure boundaries, a hallmark of physicalism as a philosophical disposition. For instance, boundaries in STEM fields are often stated by precising definitions or are incorporated into operational definitions. In CAD, a screw may have a dimension listed with a tolerance measurement. Thus, everything inside the measurement, made of metal is the screw, and everything outside the measurement and not made of metal is not the screw.
But an astute student will start asking some clever questions. What about rust? If an iron screw IS the object and the atmosphere around it is NOT the object, when the oxygen combines with the iron, is that corrosion part of the screw or something external to it? Again, pragmatically, we can tap the screw, and whatever is left after the rust flakes off can be divided into screw and not-screw. This is fantastically useful, and has been going on more or less since Aristotle. But even with this physicalist philosophy, problems emerge. For instance, it turns out, that particles are also waves with an infinite distribution through space existing as a distortion in a field. To a philosopher of physics, then, objects can't be measured with certainty because they have inherently fuzzy, probabilistic boundaries. Stranger still, wave forms have the ability to pass through 'solid' boundaries as in quantum tunneling. From WP:
Some authors also identify the mere penetration of the wave function into the barrier, without transmission on the other side as a tunneling effect.
Hence, in this sense, spatiotemporal boundaries of objects are fuzzy and overlapping, more like sound waves that blend together as in a conversation, than legos that neatly compartmentalize into set-theoretic partitions.
Questions of Discernment and Membership and Normativity
Talking again about noses, does everyone have the same definition of a nose? Does an ear-nose-throat doctor conceive of a nose in a fundamentally different way? Yes and no. Again, where is the boundary between the nose and the rest of the face? Here we see elements of the sorites paradox. In the explanation, the question is when does a grain of sand become a pile of sand by the addition of more grains? Easily one grain is not, and many are, but at some point, when does the pile exist? Two grains? Ten? One thousand? Now here's the difficult part of some people to grasp.
The simple answer is that the object 'pile of sand' is somewhat arbitrary. For one who pours concrete, a pile might measured in pounds, and for a manufacturer of sandpaper, maybe in fractions of an ounce. In a sense, a pile of sand is very intuitive, and any attempts to explain what a pile of sand is a convention and therefore normative. But you object! Clearly a pile of sand is a physical object, and everyone knows that objectivity means there must be one agreed upon object, else objects are subjective. Welcome to philosophy and please take moment to review this article on intersubjectivity. In a sense, definitions of even physical objects are actually intersubjective, because language itself is normative.
But that can't be! A car is a car is a car. A game is a game is a game. Yes, and no. (Also, meet another philosophical friend called dialetheism.) Besides mind-boggling quantum physics, philosophers of the twentieth century began exploring language in more depth realizing that categorizing groups of object is likewise mercurial. Leading the charge is Ludwig Wittgenstein and his notion of family resemblance. And from that, the science of language has produced the idea of the prototypical definition along with fuzzy logic have blurred the lines of identity and membership quite literally.
What an object is and isn't to some extent is a convention. The best way to simplify that idea is to use the example of a picture of a red apple on a green background. Can you picture it? The apple is the red pigment and the green pigment is the field. But no one can really draw an exact line between the two. Anytime one zooms in and attempts with a finer pen, someone else can zoom in more and find a better outline, until ultimately, one is dealing with molecules and atoms who have no distinct boundaries. (Orbitals of electrons, the "outside" of a molecule in the modern sense, are probability distributions of wave functions.) But as much as people might dispute the boundary (philosophers in our extended metaphor), most people get a long quite fine, right? That's because most people just agree to agree there's some red and its not green. Unfortunately for red-green colorblind people, sometimes the community fails to see that their "objectively real" red apple isn't even visible to a minority. They might mock them, might tell them they're crazy or stupid not realizing the object "apple" is actually a convention of language that a person who can't experience it is blind to. In this way, even ordinary objects (SEP) are difficult to explain.
As a physicist, and from that perspective only, the question is arbitrary. Within a system, in physics, we often 'draw' imagined dotted lines around parts of that system and regard them as independent, separate entities - and then seek the rules that apply to each individual element. In this way, the system (or object), becomes a combination of parts. And each part, or element, can be regarded as a separate entity, consisting of that which is within the 'dotted line' and that which is without. i.e. what is without the dotted line is the entire universe!
So a rusty nail could become i. The intact metal, surrounded by a dotted line, interacting with the rest of the universe. (Likely the rust layer) ii. A rust layer, again bounded by an imaginary dotted line, interacting with the rest of the universe (e.g. the intact metal, and the atmosphere, and iii. the rest of the universe. As such, there is no real need to define a single object.
The obvious thing is that there is no clear boundary.
The case of living organisms in this discussion is particularly interesting. I am Peter, a material "object", in a broader sense. But what exactly is part of me? My skin? My hair (which is dead matter)? My saliva? The urine in my bladder? The contents of my intestines? The microbiome thriving in it, and on my skin? "The human body contains trillions of microorganisms — outnumbering human cells by 10 to 1. " Many of them are essential for my well-being, and a pre-modern description of "self" would probably count all of that as part of a person because it resides within the physical boundary of their body. But being modern, we may not consider the urine an actual part of the organism. But then, why should the blood in my veins be?
If we think that objects should be somewhat persistent through time, things become even more complicated with organisms because they exchange large parts of their constituting matter over time. This leaves us in a "Ship of Theseus" situation. Heraclitus was fully aware of it: We never step in the same river twice, but we also never talk to the same person twice.
So if the boundaries of a living being are so ill-defined in terms of a physical object, what are we? Why can we maintain such a strong sense of identity? What, in the sense of the word, defines us?
The invariant which is maintained — which constitutes our identity — is our structure. The connections our brain has formed, the placement and shape of our body parts, the memories of past infections imprinted in our T-cells. Our DNA. We are not a specific lump of matter: We are a self-replicating pattern traveling through time. We are a resonance imprinted on matter rather than a fixed, static "object".
Structures, patterns that share commonalities independent of the specific underlying "substrate" they emerge from, have been recognized as their own field of research — Systems Theory — only in the 20th century.
This angle which looks at structures rather than matter, relations rather than entities, closes the circle and allows us to answer the original question:
Objects are systems.
A system is a collection of interacting parts whose inner coherence is strong compared to its connections to its environment. That's something all trivial objects — stone, paper, scissors — share: We can pick them up and they retain coherence; we can move them more or less in one piece and put them back down. There is no need to be absolute here: I lose a few molecules of myself wherever I am, but it's really little compared to the other 1028 molecules that stick together really well, microbes or not.
This definition works very well for inanimate objects as well: A handful of powder snow is probably not an object: Its inner coherence is too low. A snowball though is, until its existence comes to an end in somebody's face. A wooden plank is an object as soon as we have separated it from the trunk of a tree, but not earlier when its coherence with its surroundings was too strong.
The systemic approach is fertile. It allows us to recognize certain collections of objects as single objects, something a purely static approach may have trouble to justify: Particles form atoms, atoms form molecules, molecules form cells, cells form complex organisms, organisms form hives, states and peoples. We are part of a planet, part of a solar system which is clearly an object even though the coherence is entirely immaterial, because it is still relatively strong compared to its interactions with its surroundings. The same is true for the Milky Way, our local group and ultimately, presumably, the universe.
Objects which consist of interacting components are called systems. A car object is a system since it has many components like the breaking system, the engine, the indicating system.etc. Similarly an atom is a system since it contains protons, neutrons and electrons. Whether you interpret the object in question as a whole or as a system is up to you. You can interpret a car as a whole where it has functions like allowing you to get to work, or you can interpret it as a system where it consists of differing components interacting. Each component of a system can also be interpreted in the same way, as a whole or as a system itself, in this way systems are said to be hierarchic.
So an answer to the question of where the boundary is, is that there isn't one uniform way of determining where it is because systems can be quite abstract themselves. For example your TV set is a system which consists of a remote control and a set-top box, these two objects are clearly not phyisically near each other but are still a system that could be considered as one.
Here is a good description of systems https://www.scq.ubc.ca/systems-biology-an-overview/