"4 How can you think of saying to your friend,* `Let me help you get rid of that speck in your eye,' when you can't see past the log in your own eye?"
a : at the farther side of : beyond
More: Past - Definition and More from the Free Merriam-Webster Dictionary
prep. More: past - definition of past by the Free Online Dictionary, Thesaurus and Encyclopedia.
2. Beyond in position; farther than: The house is a mile past the first stoplight. They walked past the memorial in silence.
- beyond in place or position ⇒ the library is past the church
More: Definition of past | Collins English Dictionary
To be honest with you, I couldn’t make head nor tail of the underlined part. In other words, I couldn't analyze it. Surfing the Net looking for "can't see past" and replied, "can't see past the end of nose." In a word, does the word past in the underlined part function as a preposition? Will you help me make it clear, please?