But that fails to take into account the many ways we have learned of since then where matter does not “have a tendency to combine in small whole-number ratios”. Neutron stars are massive quantities of substance, form naturally, and are composed of things with approximately the mass of a hydrogen atom, but almost none of its other properties. An alpha particle (He-4 nucleus) is similarly reminiscent of a helium atom, but exhibits significantly different properties; a beta particle (free electron) bears no resemblance in mass or behavior to any atom. Despite this, both are naturally occurring “substances” (here “substance” is defined as “quantity of matter”).
Heck, even atoms do not exhibit the same properties; a large collection of atoms which have higher-energy electron orbits than their base state will emit photons while they tend back toward that base state, but a large collection of naturally-occurring Hydrogen will include some Deuterium (which is stable and has most of the properties of hydrogen except its mass) and some Tritium which still chemically resembles Hydrogen (despite being about three times its mass) until at some point it spontaneously transmutes into Helium-3 and gains an entirely new set of chemical properties. Modern chemists consider the typical behavior of atoms a useful approximation in many contexts, but that doesn’t make it “pretty damn certain”.
But that fails to take into account the many ways we have learned of since then where matter does not “have a tendency to combine in small whole-number ratios”. Neutron stars are massive quantities of substance, form naturally, and are composed of things with approximately the mass of a hydrogen atom, but almost none of its other properties. An alpha particle (He-4 nucleus) is similarly reminiscent of a helium atom, but exhibits significantly different properties; a beta particle (free electron) bears no resemblance in mass or behavior to any atom. Despite this, both are naturally occurring “substances” (here “substance” is defined as “quantity of matter”).
Heck, even atoms do not exhibit the same properties; a large collection of atoms which have higher-energy electron orbits than their base state will emit photons while they tend back toward that base state, but a large collection of naturally-occurring Hydrogen will include some Deuterium (which is stable and has most of the properties of hydrogen except its mass) and some Tritium which still chemically resembles Hydrogen (despite being about three times its mass) until at some point it spontaneously transmutes into Helium-3 and gains an entirely new set of chemical properties. Modern chemists consider the typical behavior of atoms a useful approximation in many contexts, but that doesn’t make it “pretty damn certain”.