In speaking of Karma and Conditions the following is presented in "WHAT THE BUDDHA SAID":
Any shift in any fashion in the conditions up or down or across the stream
relative to the cause will impact the resultant outcome of that cause.
How do we know this? Just go back to the Albert Einstein analogy found in What the Buddha Said where he, Einstein, just 'intuitively figured it out.' Over periods of thousands and thousands of years observant people have seen rise to the same thing over and over and have placed words around the phenomenons observed.
David Hume (1711-1776) discussed the exact same problem in his book An Inquiry Concerning Human Understanding. He said knowledge is not attained by reasoning a priori, but arises entirely from experience, when we find that any particular objects (or phenomenon) are constantly conjoined with each other:
I have found that such an object has always been attended with such an effect and I foresee that other objects which are in appearance similar will be attended with similar effects. ... The connection between these propositions is not intuitive. There is required a medium which may enable the mind to draw such an inference, if indeed it be drawn by reasoning and argument....
In reality, all arguments from experience are founded on the similarity which we discover among natural objects, and by which we are induced to expect effects similar to those which we have found to follow from such objects. And though none but a fool or madman will ever pretend to dispute the authority of experience, or to reject that great guide of human life, it may surely be allowed a philosopher to have so much curiosity at least as to examine the principle of human nature, which gives this mighty authority to experience, and makes us draw advantage from that similarity which nature has placed among different objects. From causes which appear similar, we expect similar effects....
When a man says, I have found, in all past instances, such sensible qualities, conjoined with such secret powers, and when he says, similar sensible qualities will always be conjoined with similar secret powers, he is not guilty of a tautology, nor are these propositions in any respect the same.
For an interesting comparison take the above written by Hume and match it with the centuries old Sanskirt insights and meaning behind the word Upamana
WHAT THE BUDDHA SAID
WHAT THE BUDDHA TAUGHT
ON THE RAZOR'S
(David Hume, An Inquiry Concerning Human Understanding, The Liberal Arts Press, 1955, pp.42-53 )