I came across those arguments sixty years ago - one of our chemistry lecturers was a Christadelphian. also a fellow student.
Solomon in Ecclesiastes is speaking apparently with authority, with God-given wisdom, so how can we question his assertions?
Read Ecclesiastes 1 to see his basic premise - to explore by wisdom all that is done under heaven. ... under the sun.
He is deliberately limiting his quest to what can be found by observation rather than divine revelation. He is reasoning like an atheist philosopher and comes to the conclusion - everything is meaningless.
When he brings the Creator into consideration, his conclusion is - fear God..... and he also wrote Proverbs.
Ecclesiastes:
Here is the verse and some immediate context:
Ecclesiastes 9:5 KJB - For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten.
Ecclesiastes 9:6 KJB - Also their love, and their hatred, and their envy, is now perished; neither have they any more a portion for ever in any [thing] that is done under the sun.
Ecclesiastes 9:10 KJB - Whatsoever thy hand findeth to do, do [it] with thy might; for [there is] no work, nor device, nor knowledge, nor wisdom, in the grave, whither thou goest.
According to these texts of Scripture, written by Solomon, under the inspiration of the Holy Spirit:
2 Timothy 3:16 KJB - All scripture [is] given by inspiration of God, and [is] profitable for doctrine, for reproof, for correction, for instruction in righteousness:
2 Peter 1:21 KJB - For the prophecy came not in old time by the will of man: but holy men of God spake [as they were] moved by the Holy Ghost.
We see that the texts under immediate consideration say:
1. The living "know" that they shall die
2. the dead "know" not anything
Only those which bypass the first part, attempt to negate the second. For if they attempt to say that the dead really do know something, which is polar opposite of the text, it would also have to reverse the first portion, meaning that the living do not know that they are going to die, and is pure contradiction to all of Scripture.
Then consider the next portion, speaking of the "dead" which "know not anything", for even:
1. "Also their love, and their hatred, and their envy, is now perished"
The Hebrew word "אָבַד", Transliterated: "'abad", in English - "perished", means gone, not, ceased to be, blot out, exterminate, destroy, kill, put to death - source Strong's Concordance.
Now, consider the latter text, and see yet one further aspect:
1. while living do everything with one's "might" given them of God
2a. because in death, "for [there is] no work, nor device, nor knowledge, nor wisdom"
and yet further, the text clearly reveals that it is to the grave that mankind in their death go:
2b. "in the grave, whither thou goest"
Yet, some will attempt to address the whole of Ecclesiastes with a wave of the hand by disparaging Solomon or the words therein. One ought to remember Who it was that actually inspired this "Preacher" and his words - Ecclesiastes 1:1.
One must remember, that this "Preacher" is the type of Christ Jesus. For Solomon, whose name means the "Peace", is the "Son of David", the "wise" one who built the Temple of the Lord and reigned in Glory like no other King. Jesus said:
John 5:39 KJB - Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
Therefore, let us not so readily dismiss or disparage the words in Ecclesiastes as of one which is simply speaking of melancholy, for he is not. Iit truly is a sermon from the "Preacher", who is indeed "wise" which taught the people "knowledge", not "vanity":
Ecclesiastes 12:9 KJB - And moreover, because the preacher was wise, he still taught the people knowledge; yea, he gave good heed, and sought out, [and] set in order many proverbs.
In fact, the last words of Ecclesiastes actually sum it all up for us:
Ecclesiastes 12:10 KJB - The preacher sought to find out acceptable words: and [that which was] written [was] upright, [even] words of truth.
Ecclesiastes 12:11 KJB - The words of the wise [are] as goads, and as nails fastened [by] the masters of assemblies, [which] are given from one shepherd.
Ecclesiastes 12:12 KJB - And further, by these, my son, be admonished: of making many books [there is] no end; and much study [is] a weariness of the flesh.
Ecclesiastes 12:13 KJB - Let us hear the conclusion of the whole matter: Fear God, and keep his commandments: for this [is] the whole [duty] of man.
Ecclesiastes 12:14 KJB - For God shall bring every work into judgment, with every secret thing, whether [it be] good, or whether [it be] evil.
Solomon gave us
"acceptable words", even wrote that which was
"upright" and not fallen, yes even,
"words of Truth". These, says he, are
"words of the wise", being
"goads" and were as
"nails" of the
"masters of assemblies", and
"given from one Shepherd" - Jesus Christ.
Solomon says,
"be admonished" by these words, and then says, "Let us hear the conclusion of the whole matter".
"Fear God".
"keep His commandments" - which "is the whole [duty] of mankind/Adam".
Why?
For men will be judged by the Commandments of God, and God will bring every work of men/Adam into that Judgment.
What is more amazing, is that after many 'throw Solomon under the bus' for being melancholy, attempting to remove the words spoken that the "dead know not anything", they turn right around and use this verse:
Ecclesiastes 12:7 KJB - Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.
In the very same book, which they speak so poorly of, in the previous verses, to attempt to justify the satanic/pagan/occult - Gen. 3:4 belief that the "dead" somehow are inherently immortal and alive somewhere.
Yet, even that verse does not teach what they would desire of it. For notice that "the dust" which we/mankind is taken from - Gen. 2:7, returns to "dust", the "earth" even "as it was", and the "spirit" or "breath of life of God", which is His, not ours, returns unto Him.
We do not "return" unto Him [He has to come for us all together [John 14:1-4 KJB], for we are "dust" and to "dust we shall return":
Genesis 3:19 KJB - In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou [art], and unto dust shalt thou return.
Yet, they will refuse such plain passages, and declare 'no!' the "spirit' which 'we are' returns unto God, and therefore, the text not allowing any distinction, also allow even the wicked to return unto Heaven by their saying, for that is where God is, and the occult use the text in such a manner to say Hitler, Mussolini, Stalin, Marx, etc are in Heaven, and so on:
"Father which is in heaven".
Solomon was not merely speaking of the righteous, but all men which die.
Proverbs 8:7 KJB - For my mouth shall speak truth; and wickedness [is] an abomination to my lips.