However as a complete view of all truth I believe these philosophies are fatally flawed.
As they limit truth by the limitations of our ability to observe and measure and how we can logically deduce..
Maybe, but if you can't measure something or its effect on its surroundings, it probably is not there.
As we know that as humans we cannot measure all of reality and we our minds and limited and we cannot rationalise all things. So to limit truth to our ability would seem somewhat limited..
But what do you mean by this? If it exists it can be measured.
Was electricity not true till we discovered the voltmeter?.
Not sure of yourpoint here, but clearly electricity existed before the voltmeter of course.
Was Newtonian physics true until Einstein developed his theory?.
Newtonian physics was indeed an excellent approximation to observable reality. It only really breaks down in extremely strong gravitational fields. But is/was still accurate enough to enable mankind to put a man on the moon. Einsteins relativity superceded Newton and has been proved time and time again. Although it is noteworthy to mention at this point that newtons never really worked where mercury was concerned. This fact was conveniently ignored for a long time because everything else seemed to work and fit so well. This is of course the nature of science, first you hypothesise, then you test, and test, and test.
I am not arguing against these philosophies are useless, they have there place in science, but to try and understand all of reality with such limited tools seems foolish to me.
Again, not sure what you mean by limited?
I would assert that if something exists we should be able to measure it. If not then it is probably not there.
Thanks
Robert.