Romans 1:20 (NASB)
For since the
creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that
they are without excuse.
Here we see that "the world" is without excuse. Therefore by logical necessity, the world refers to mankind, and not inorganic material which has no understanding of God's invisible attributes. For that it takes a mind with the capacity to engage in abstract thinking.
Turning to the more difficult interpretation:
Matthew 13:35
This was to fulfill what was spoken through the prophet:
“I WILL OPEN MY MOUTH IN PARABLES;
I WILL UTTER
THINGS HIDDEN SINCE
THE FOUNDATION OF THE WORLD.”
There are at least three differing interpretations of "the foundation of the world." First, the phrase might refer to God's creation of our solar system. Thus the origin of our planet earth usually said to mean the creation. Second, the "world" might refer to mankind, and thus refers to God's creation of mankind. The third view is "the world" refers to "fallen mankind" and thus refers to after or since Adam's fall.
But if you ask, from whom were things hidden, again you must say hidden from people with the capacity to engage in abstract thinking. So the second or third view is correct based on Matthew 13:35.
But let us look at one more verse:
Hebrews 4:3 (NASB)
For we who have believed enter that rest, just as He has said,
“AS I SWORE IN MY WRATH,
THEY SHALL NOT ENTER MY REST,”
although
His works were finished from the foundation of the world.
Here unless we think God's works included the fall (Adam's volitional sin), we conclude the second view, the creation of mankind (Adam of Eve) is what "the foundation of the world" refers to.
As a side note, when considering the meaning of a word or phrase, we need to study and consider alternative possibilities of every single usage in scripture, or if the number is too high, the usages by the same inspired author or in the same book.
