Unfortunately, this belief is not only untrue, it couldn't possibly be true. In order to do science the scientist must make a host of metaphysical assumptions, and moreover, many of the theories that pass as science and are taught in schools are more metaphysical than they are empirical. Here's a partial list of some of the things that either many scientists believe or that all scientists pretty much must believe, and none of them are themselves scientific. That is to say there's no way to verify or to falsify any of them:
1. The Many Worlds Hypothesis: The idea that ours is just one of a nearly infinite number of universes, all of which are closed off from each other thus defying detection.
2. The Oscillating Universe Hypothesis: The theory that our universe has expanded and collapsed an infinite number of times.
3. String theory: The idea that the fundamental units of material substance are unimaginably tiny vibrating filaments of energy.
4. The existence of other dimensions: The theory that the four dimensions of space-time are only part of physical reality.
5. Principle of Uniformity: The assumption that the laws and properties of the universe are homogenous and constant everywhere throughout the cosmos.
6. Assumption of Uniformitarianism: The idea that the same processes and forces at work in the world today have always been at work at essentially the same rates.
7. The Scientific Method: The idea that there is a particular methodology that defines the scientific process and which ought to be followed.
8. The Law of Parsimony: The principle that assumes that the simplest explanation which fits all the facts is the best.
9. The assumption that human reason is trustworthy: The notion that a faculty which has evolved because it made us better fit to survive is also a dependable guide to something else, truth, which has no necessary connection to human survival.
10. The assumption that we should value truth: The idea that truth should be esteemed more highly than competing values, like, for instance, personal comfort or group advancement.
11. The preference in science for naturalistic explanations: This is a preference based upon an untestable assumption that all knowable truth is found only in the natural realm.
12. Naturalistic Abiogenesis: The belief that natural forces are sufficient in themselves to have produced life.
13. The assumption that if something is physically possible and mathematically elegant then, given the age of the universe, it probably happened.
14. The assumption that the cosmos is atelic. I.e. that it has no purpose.
15. The assumption that there's a world external to our own minds.
16. Materialistic Reductionism: The conviction that all phenomena, including mental phenomena, can be ultimately explained solely in terms of physics and chemistry.
17. Assumption that the universe arose out of a "vacuum matrix" rather than out of nothing.
18. Ethical claims regarding the environment, nuclear power, cloning, or genetic engineering.
19. The Concept of the Meme: According to biologist Richard Dawkins memes are the cultural analog to genes. They are ideas or customs that are believed by Dawkins and others to get passed along according to their survival value rather than their truth value (see #9, above). An example of this, unfortunately, is the concept of the meme itself.
20. The criteria by which we distinguish science from non-science.
21. The assumption that science is the only way, or at least the best way, to arrive at truth.
Mention of none of these in public school science classrooms precipitates the levitation of a single eyebrow among the custodians of science purity yet every one of them is a matter of metaphysical preference, not empirical fact. Why, then, do those custodians suddenly wax squeamish when the topic of discussion turns to the possibility that incredibly complex information-based systems in the living cell are the product of intentional engineering? Why are some metaphysical claims permitted and others not?
