As for how one explains that Ecclesiastes chapter 9 is not meant to be taken as the final word on death and the Grave, one needs only use the Jehovah’s Witnesses’ own New World Translation, 2013 Revision to show them the following:
According to the Bible, when Jonah was swallowed by the big fish he prayed the following:
Out of my distress I called out to Jehovah, and he answered me.
Out of the depths of the Grave I cried for help.
You heard my voice*.–Jonah 2:2*.
Of the word “Grave” in this verse, the footnote to the 2013 revision of the NWT states:
Or “Sheol,” that is, the common grave of mankind. See Glossary.
When one looks up the “Glossary Term,” the New World Translation, 2013 eevised edition states:
When lowercased, referring to an individual grave; when capitalized, the common grave of mankind.
Jonah was not in “an individual grave,” but as the New World Translation points out by using a capital “G” in the word “Grave,” Jonah was conscious in the “common grave of mankind.”
This is obviously further revelation that adds to what we read in Ecclesiastes 9:10:
There is no work nor planning nor knowledge nor wisdom in the Grave.
According to ancient tradition that was written in the time of Solomon who reigned circa 970 to 931 BCE. But Jonah lived during the reign of Jeroboam II, circa 786-746 BCE. Accordingly we must surmise that the Jews understanding of what could and could not happen in the Grave had increased to include the activity of consciousness and prayer by the time the words of Jonah were penned.
This would make sense since Proverbs 4:18 states: “The path of the righteous is like the bright morning light that grows brighter and brighter until full daylight.” So it should not surprise us that while in Solomon’s day it was taught that there was no consciousness in the Grave, some 184 years later this had changed to state that prayer from the Grave could and did indeed occur. This is not a contradiction but a demonstration of how God revealed the truth to his people step-by-step, century by century even in Bible times.
While the parable of the Rich Man and Lazarus is not to be taken literally, Jesus did not invent the scenario of a conversation among the dead. Jesus always used symbols in his parables that the Jews of his time were familiar with, and the parable of the Rich Man and Lazarus is not any different. At least to some of the Jews a “discussion” in the Grave wasn’t anymore far-fetched than Jonah’s prayer from the Grave.
During the time of Jesus the Jews had various opinions on life after death. The Pharisees believed in the physical resurrection of the body at the end of time, the Essenes believed in the immortality of the soul, while the Sadducees believed in neither of these concepts. Only the Sadducees held a view in line with the words of Ecclesiastes chapter 9, but they were condemned by Jesus who told them about their view of death: “You are misled because you do not know the scriptures or the power of God.”–Matthew 22:29, NABRE.
Consciousness can indeed occur in the “common grave of mankind” because people can even be living upon entering the Grave. Why Number 16:33 states: “So they and all who belonged to them went down alive into the Grave.” People who are alive can think, pray, talk, etc.
What Ecclesiastes is speaking about is not a contradiction because when one takes the book as a whole it speaks about life from an earthly perspective. The author repeatedly states that “Everything is futile!” Of course he is speaking only figuratively because life and its experiences are not truly futile. Without God to intervene, however, life that leads to the Grave is futile indeed–and this is what it looked like for humankind prior to the arrival of Jesus Christ. Once Christ came this changed, and even death was transformed.–See Colossians 3:3.
Will we be like the Sadducees who hung on to a view that got condemned by Jesus? Or will we accept the words of a prophet like Jonah and the text of the New World Translation that shows that conscious prayer does occur in the “common grave of mankind”?
So Jesus was not inventing something new when he described the Rich Man and Lazarus as “conscious” after death. It was totally in line with what God revealed through the experience of Jonah the prophet.