The majority of Karl Popper’s beliefs can be summarized in one theory – the theory of falsifiability. Popper was the first philosopher to popularize falsifiability, as well as apply in a more general fashion to a greater field of science.
For a statement to be “falsifiable”, it must be inherently confirmable or verifiable by experiment or observation. For example, the statement “All left handed people are evil” is not falsifiable, because it cannot be definitively decided whether all left handed people are evil. A statement that may be falsifiable is “all left handed people have blue eyes”. It is falsifiable because you can simply disprove this statement by finding a left handed person who does not have blue eyes.
Karl Popper believed that in order for us to accept science as truth, the science must have falsifiable properties, but not yet have been falsified.
And for the time being, this assertion was valid (even though it was more of a social-science question) and therefore was not wrong (and as close to ‘true’ as true can get) according to falsifiability. However…
In Popper’s view, when science follows a rigorous and systematic approach to knowledge based upon simple and repeated observation we, as humans come as close as we possibly can to being objective. Repeated observation of a certain phenomenon (like gravity, or in the previous example, the type of politicians elected) without any exceptions or deviations allows us to form a hypothesis and so long as said hypothesis is disprovable, and has yet to be disproved, then people are conducting things in the most objective way possible. It would be hard to argue that some force (gravity) is not keeping things together. If you were living a few hundred years earlier (before women’s suffrage), it would have been equally as true that human only ever elected white males to political office, until of course a non white/female become elected and tosses your theory out the window.
Popper’s theory, however, still leaves room for that one exception to your rule that could make it completely irrelevant. This ensures that if our theories are trapped in one of Plato’s caves (inside a cave inside a cave), there is still a built-in escape clause in falsifiability that allows us to reject theories that have been disproven. Falsifiability does not, however run into the post modernist problem of questioning everything because it says that if something has yet to be disproven (and can be disproven) then it is good enough to work until such a point that it becomes invalidated.
Therefore, Popper and his theory of falsifiability dictate that something can’t be proven true, only not false. However, if something resists being proven not false for long enough after significant attempt, then it approaches being “true” and “objective” but never quite gets there. Since objectivity relies on absolute truths, science can not be truly objective, but it can be very close.