Science vs. Metaphysics
Some things can be predicted with certainty, other things can not. The difference between science and metaphysics is very simple – for science, the end is contained in the beginning; for metaphysics, the end is open. It is a valuable concept to understand.
When what will happen at a particular moment in time can be predicted, that event might as well have already happened. Throw a ball in the air, at a given velocity, and a simple physics formula will tell you when and where it will land. Its landing spot is decided the moment it leaves your hand – the beginning contains the end. This is what science strives toward: to study reality in order to predict it, to predict reality in order to control it.
Science is based on some assumptions and suppositions. It assumes, for instance, that reality exists. It seeks to understand and control the organizing forces of reality. Thus, it assumes such organizing, but rarely enters into the quest for the source of such organization... the organizer. Science frequently measures states of change in units of time and space. Science has always assumed the existence of space and time and until recently has had to ignore the paradox of space and time, position and momentum.
Metaphysics is concerned with the 'biggest questions' - the meta-questions. Its primary question is "What exists? And what is it like?"
From this question, arise questions such as: What is it like to exist/not exist? Does reality exist? If so, what is it like when reality does not exist? What is the source of reality? What is time? What is beyond time, or non-time? Do humans have free will? The developmental psychologists among you will recognize these questions, as those of a precocious pre-schooler.
Metaphysics is notoriously difficult to define, but for purposes of briefly introducing it, it can be identified as the study of any of the most fundamental concepts and beliefs about the basic nature of reality, on which many other concepts and beliefs rest—concepts such as being, existence, universal, property, relation, causation, space, time, event, absolute, and many others.
Some of the difficulty with defining metaphysics lies in how much the field has changed since it was first given its name by Aristotle's editors centuries ago.. Questions, which were not originally considered metaphysical, have been added to metaphysics. Other questions that were considered metaphysical questions for centuries are now typically relegated to their own separate subheadings in philosophy, such as philosophy of religion, philosophy of mind, philosophy of perception, philosophy of language, and philosophy of science.
The core metaphysical questions would be the ones which have always been considered metaphysical and which have never been considered not metaphysical. What most of such questions have in common is that they are the questions of ontology, "the science of being qua being"... otherwise stated as, "I Am that I Am", or more clearly, "OM"