"the study of the fundamental nature of knowledge, reality, and existence"
The hard sciences endeavor to explain and understand the mechanisms of nature, how they work and what they are made of. Philosophy goes beyond physics and chemistry and asks a deeper question then how or what, and that is why? Why is there something rather than nothing? Philosophy also examines the structures of arguments and reasoning from the data the hard sciences produce.
Without logical reasoning, it is very hard to discover and argue truth. When I say argue I don't mean quarrel, I mean presenting reasons that support a conclusion. We are living in a day when many are forgoing logical reasoning and researching truth and promoting assertions because they go along with their world views.
It is important to have good reasons to believe what you believe or else you are no more convincing than Monte Python below.