Naturalist stochastic

In a very general sense, modern science assumes that everything that happens, has happened and ever will happen is a result of random occurrences within ranges of probability. Like, for example, whether a coin flipped into the air will land heads up or tails up. It's a matter of pure chance in which the range of probability is 50-50. It's random, or stochastic.
The ranges of probability are framed by what are still called the "physical laws" of the universe. This phrase could cause a lot of trouble for us if we ask too many questions about what it means, exactly. So we won't go there right now.
But for an example of the stochastic universe that does not involve a penny, take the origin of life. It is generally believed that life began by chance. Certain chemicals mixed together and formed more complex chemicals called amino acids. The amino acids because of certain pre-existing physical laws complexified, and by chance - possibly a lightning bolt in a certain place on Earth at a certain moment around 4 billion years ago - became electrified and were jolted into life. Which is to say, a self-replicating set of chemicals. This is thought to have happened by accident. The probability of it is astronomically low, approaching the range of impossible. But obviously, it did.
For about 3 billion years, there was not much change in the self-replicating systems, which is to say, bacteria and algae. Then some unknown, unexplained event happened by accident and the single-celled systems began to complexify into multicelled systems. After that all hell broke loose. Accident after accident happened, which in evolutionary theory is called mutation, and the single-celled bacteria began turning into plankton, grass, clams, dragonflies, dinosaurs, fish, roses, rattlesnakes, kangaroos, pine trees and humans. Not necessarily in that order.
Somewhere in there - we have no way of knowing when because we have no direct experience or evidence of what animals other than humans actually experience - a very complex thing popped into existence: awareness. Since (it is assumed) every development that came before it resulted from chemical changes, it is also assumed that awareness is a byproduct of chemicals firing in your brain. There is a name for this assumption. It is called "epiphenomenalism."
Epiphenomenalism makes sense to most scientists because to them it's self-evident that everything is a physical process. What else is there? First there was energy. Then the energy accidentally coalesced into physical particles. Then the particles accidentally began channeling energy. Then the interactions between channeling particles became so complicated that they became aware of themselves. I.e., you reading these words.
One trouble with this way of looking at the world is that it means you personally - the you that is having experiences and is aware of it - do not actually exist. You are just chemicals going off and creating the illusion that you are something, when really you are nothing, just chemicals and accidents. You are not making any decisions about what you do, say or think. Chemicals are doing that, and creating the illusion that you are doing it.
To rephrase the warning of one botanical scientist, it is important to remember that a human being is nothing more than a cluster of nerve, blood and flesh cells channeling energy in a way that accidentally allows them to perceive and analyze their surroundings and seem to appreciate them. There is no such thing as you, there is no such thing as beauty, and there is no such thing as "right" or "wrong" because you are not doing anything, chemicals are.
And it's kind of silly to wonder where those pre-existing physical laws came from. It's all just accidents waiting to happen.