The world is composed of distinct, identifiable materials. Stuff is not one continuous thing; it is made of individual, separate, discrete things that are observable, identifiable, and distinguishable from one another. This is the second foundational assumption.
Our World is composed of matter. That immediately raises the question: how can all this diversity, interaction, balance, and all that makes this system the dynamic thing it is, be made of just one thing? Yet every thing, every happening, every phenomenon happens because things in our world are composed of matter. The winds that blow, the snows that fall, the rocks that erode, the metal that rusts, the flowers that bloom, the flock of birds that fly, the city that thrives: all happen in association with matter.
Material is the name of a class. There are no entities whose name is material; no physical object carries that as its name. Materials are names of groups of individual things, where the members of a class share a feature or characteristic in common. We see this water and that water, the river and the cloud, and we group them under the class material called water. The material exists; the class is how we organize what exists.
If the world were one continuous, indistinguishable substance, there would be nothing for chemistry to describe. The fact that the world is composed of distinct identifiable things is what gives chemistry its subject. The diversity of materials, and the differences between them, is the start. From here, observation, characterization, and the discovery of properties become possible.
Question
How can all this diversity, interaction, and balance be made of just one thing, matter?
Reveal Merrill's answer →Hide answer
The diversity is in the materials, not in the matter. Matter is the underlying stuff; materials are the distinct, observable things matter forms. Macroscopic chemistry studies the materials and how they behave, leaving the question of what matter ultimately is to other inquiries.