Empiricism is a basic way of explaining the nature of reality, & as such, it dictates virtually everything a person believes. For this reason, it's the first philosophical topic I tackle, since it underlies everything else I write.
Generally speaking, my viewpoint is an empirical one, for reasons which I'll explain. My own views, however, may not entirely coincide with that of what is called "empiricism" by some philosophers.
This, of course, is rather intuitive. Take a sealed box, for example. Assume that an object is in it. You cannot see the object, but it is there, nonetheless, & you'll see it, as soon as you open the box. The object exists, regardless of the fact that it cannot be seen. Its existence doesn't depend on it being seen or sensed in any other way.
We all must learn this, however. Infants do not understand that things they cannot see, hear or touch, may still exist. This is why babies sometimes cry when their mother leaves the room — they think that mother is "gone," for good. When mother reappears to calm them, they're happy again. It takes some time for infants to absorb the fact that things may still exist, even if they can't be sensed.
This is, perhaps, the most important fact that we as humans can learn, & is so basic to our thinking, that it took thousands of years for anyone to question it.
There are also ways in which we can perceive things which have no measurable, physical reality. We can imagine things, for one; Æsop's fables, for example, are full of talking animals & other things which we know cannot actually exist. (At least, no one has shown that they exist, & from what we know, we can safely surmise that no one ever will.)
For another thing, we can dream. While we're dreaming, in fact, we believe that the inventions of our sleeping brains are real. Only after waking, do we see that they aren't real. (Lucid dreams, or dreams in which one is aware that one is dreaming, are certainly possible, but aren't common.)
Dreaming has been something of a problem among philosophers for a long time. How can we be sure that our "waking" lives aren't dreams? There are many who take the view that this is still possible. I may actually be sleeping, somewhere off in the cosmos, dreaming that I'm typing this into my computer. For that matter, I might be somewhere in the cosmos, dreaming that I'm dreaming this. And I might be dreaming that I'm dreaming that I'm dreaming that I'm dreaming this....
The rationalist philosopher Descartes, however, pursued this line of inquiry, to its logical conclusion. He concluded, "Cogito ergo sum," which is Latin for "I think, therefore I am." In other words, while I may not be certain that I'm dreaming, or dreaming that I'm dreaming, etc., just by virtue of the fact that I am trying to figure this out, I can be certain that — somewhere & in some form — there is a "me" who is having such thoughts.
To go back to the example of the box ... we can look at the box, touch it, shake it, & so on. It looks like other objects which we have seen in the past, objects we have come to classify under the word "box." But, we cannot be absolutely certain of the box's reality. We might, instead, be dreaming of the box. Or, the box might be some sort of complex illusion, a Star Trek-style "holodeck" object.
Furthermore, we can surmise that something is in the box; after all, the purpose of a box is to contain things. This is an order of magnitude less certain than the box's own existence, however; it may have had something at one time but is empty now, or it might be waiting to have something put in it.
As I said, however, the only thing we may be certain of is that we have had the experience of interacting with something known as a "box." Beyond that, all else is guesswork.
This is perhaps the greatest flaw in empiricism. Empirically speaking, there is little we can be absolutely certain of. Taken to extremes, empiricism tells us that nearly everything we know is uncertain, & that all knowledge is folly. In fact, this was the position of the classical Skeptics of ancient Greece; the name of this school has come to mean someone who suspects everything.
Of course, the flaw of this thinking is, if you treat all knowledge as suspect, then you must, by definition, treat as suspect the assertion that all knowledge is suspect!
The fact that empirical thinking ultimately leads to this conclusion, is seen by many as a refutation (or demonstration that it's false). "Pragmatic empiricism" is a contradiction in terms, since it's not "pure" empiricism.
There is a way, however, to show that pragmatic empiricism is a valid ideal. While I can only be certain that (1) I exist, and (2) I have experiences, there's something else I can be certain of: that (3) I exist in a context, which is a way of saying that there must be something around me, which causes me to have experiences.
Now, there is still the matter of total certainty. I might simply be dreaming that I'm typing this on my computer — that my computer doesn't actually exist. But since it appears to me that I am actually typing on a real computer, on at least some level, that is exactly what I'm doing.
So, for me to assume that the computer exists, right in front of me, is a very reasonable conclusion, based on my empirical experience.
Some would say that this uncertainty about reality is unreasonable. Why be so uncertain about things that appear real? Why deny what we can see & hear & touch? Well, that's the key! While I cannot be truly, 100% certain of what it is I'm experiencing, I know I'm experiencing something, and that's enough.
Another conclusion is that, before one accepts something as being true, or at least a safe assumption, it must be empirically demonstrable. Anything else is unworthy of one's time, since only empirical experiences are valid.
This is the basis of the modern scientific method. Theories are fine, but are only as good as the experimental data that backs them up. Some fields, such as quantum physics, are based as much on mathematics (an abstraction created by human beings, not necessarily a reflection of reality) as on measurements & data. But the mathematical equations that quantum physicists use, however, are based ultimately on experimental data, & whenever possible, the results are checked against observable phenomena. In the case of theoretical particles such as the graviton, we have yet to observe them in the laboratory or in the real world, but quantum physicists have worked out some mathematical ramifications, based on the possibility that they exist; & these conclusions can be checked out. Until their existence is confirmed, gravitons are treated only as speculative, & are not part of the "Standard Model," the "accepted" body of equations & rules of quantum physics.
So, in spite of the fact that science sometimes delves into speculation, it remains largely empirical in its basis. Most of the technological & scientific advances that have been made, are as a result of an empirical mindset (past scientists such as Galileo & Newton engaged in empirical pursuits, although they sometimes engaged in metaphysics). For example, we did not learn the exact nature of the Solar System & the orbits of the planets, until celestial mechanics was worked out by Johannes Kepler. He obtained data from Tycho Brahe, the most precise astronimical observation tables available in his day. Kepler was convinced that this data would reveal the true nature of the Solar System — he was absolutely right! Committed to the empirical view that only the observed data would describe the motions of the planets, he finally discovered that they traveled in elliptical orbits of changing speed. Until then, astronomers had only described the Solar System in terms of perfect-circle orbits of constant speed, even Copernicus & Galileo. As a result, their theories did not precisely match the observations.
The more empirical Kepler, however, worked in the opposite direction — by using the data to construct celestial mechanics, rather than speculating on celestial mechanics & then checking it against observation.
In a similar fashion, all the other great scientific discoveries have been made via empirical methodology. It was only with the advent of empiricism, that we began to have a real understanding of the universe & its ways.