The following shows the main verb in bold, and helps demonstrate the meaning of the sentence through added punctuation and rewording.
Add punctuation:
Whatever I have (up till now) accepted as, "most true and assured",
I have gotten either from the senses or through the senses.
Rearrange and reword:
Until now, all the things that I have accepted as reality,
I have gotten either from the senses or through the senses.
Simplify language:
Until now, what I considered to be true and real
was based on on the senses--either directly or indirectly.