The principles of quantum mechanics are discussed in one of the other books in The Physical World series Quantum physics: an introduction and some of its applications are described in Quantum physics of matter

The basic working philosophy of most scientists, including those who say they have no philosophy, is a kind of realism. (Philosophers recognize many shades of realism.) The three main points of this creed are:

Our senses allow us to observe a physical world, and our bodies allow us to interact with that world.

Although our perceptions may differ, we all share the same physical world, which exists independently of our observations, e.g. the same Moon is really out there for all of us, even if none of us is looking at it.

Although our actions may cause disturbances, it is possible to investigate the physical world without destroying its essential structure. We may therefore try to deduce the essential features of the physical world by combining experiment and observation with rational speculation.

One of the many astonishing features of quantum mechanics is that it calls into question some of the central ideas of this kind of realist philosophy. When speaking about the nature of the microscopic entities that are described by quantum mechanics one of the subject's pioneers said:

'...they form a world of potentialities or possibilities rather than one of things or facts.'
Werner Heisenberg

Another of the quantum pioneers put it even more simply:

'There is no quantum world.'
Niels Bohr

Let's see how such statements came to be made.
Continue on to Quantum mechanics and chance, part 2 of 3