It is important to understand that scientism is philosophical, not scientific.
Science cannot tell you whether anything beyond the laws of nature exists or not, if any form of knowledge beyond itself exists, in fact science cannot even tell you if science exists.
Science cannot talk about itself. All discussion about science, without exception, is not science, it is not scientific. It is meta-scientific, specifically it is part of philosophy of science.
When someone like Richard Dawkins talks about science (as opposed to doing science as a biologist, in which case he will be talking about genes, species and populations) he is talking as a philosopher, for which he is not even particularly qualified.
All scientists who discuss science engage in a philosophical activity. Of course many great scientists historically were also philosophers, but the majority have not been.
Just because somebody is a scientist does not mean that what he says about science - ie talking as a non-scientist - has more validity than what the first person in the street might say.
Everyone is entitled to his own beliefs, and belief in scientism and materialism is an act of faith like many others.
What is deceptive and manipulative, though, is to say or imply that, because you are a scientist, you know more about science than anybody else.
As a scientist you know more about the object of your particular field.
But discussing the nature, role and limits of science, its method, its relationship with other forms of tbeoretical activities, with religion, all this is not the object of any science but of philosophy of science.
So, unless you are qualified as a philosopher or logician, your knowledge and ideas are indeed on a par with the man in the street's.
People should beware of false authoritative claims on this subject by scientists.
There is also a contradiction here on the part of believers in scientism.
If you say that science is the only source of knowledge, you are making a statement outside the realm of science, a non-scientific statement.
So that assertion is either a non-cognitive one, like a poem or piece of music, or there is indeed knowledge which is non-scientific.
Scientific triumphalists, as Melanie Phillips calls them, have somehow managed to convince large parts of public opinion that that, in the intellectual, theoretical sphere, whatever is non-scientific is anti-scientific.
This is not true.
One of the greatest philosophers of science of contemporary times, Sir Karl Popper, created a demarcation criterion establishing that a theory, in order to be considered scientific, had to be capable of being falsified, proven false.
All theories not meeting this criterion he called 'metaphysical' theories.
Yet he showed that many metaphysical theories had been positively helping science and inspired scientific theories.
For example, the 17th-century German astronomer Johannes Kepler, a central figure in the scientific revolution, was a follower of Plotinus.
The neo-platonic theory of Plotinus was the inspiration for Kepler's laws of planetary motion in astronomy by leading him to reject Ptolemy's geocentric theory that the earth is at the centre of the universe and adopt Copernicus' heliocentrism with the sun at the centre. He then refined the latter by abandoning the Copernican theory's circulary orbits of the planets around the sun - which derived from Pythagoras' belief that the circle is the perfect geometrical shape - and introducing the elliptical orbits instead.
Science is only a method. A good, effective method, but there is nothing magical about it that should justify setting it apart, above and in contrast with all other human intellectual endeavours.
Non-science is not bad and can assist science.
Non-science is bad only when it tries to pass itself for science, in a deceiving and misleading manner, as in the case of alternative medicine, astrology, paranormal and other kinds of superstition.