Say: 'God - He guides to the truth;
and which is worthier to be followed --
He who guides to the truth,
or he who guides not unless he is guided?
What then ails you, how do you judge?
-- Sura 10:35
You would sure agree, that this verse argues that we should follow only God, because he is the one who guides to truth. And any other can only guide to truth if he himself is guided. Therefore, why rely on any other and not directly follow God?
But, this argument only holds water when we can indeed trust that God leads to truth those who trust him and doesn't deceive those who follow his words and deeds.
That they said (in boast)
"We killed Christ Jesus the son of Mary the Apostle of Allah";
but they killed him not nor crucified him
but so it was made to appear to them
and those who differ therein are full of doubts
with no (certain) knowledge but only conjecture to follow
for of a surety they killed him not.
-- Sura 4:157
WHO did make this appear to them as if Jesus was crucified? Isn't it clear that that is God's acting? Now, in this verse God does both deceive the onlookers about what is happening and then "complain" about the fact that the people believe what he has made them believe.
God made it appear as if Jesus is crucified and killed, but God shifts the blame of being ignorant and full of doubt on those who believe in what is the deed of God himself.
This testimony about God given in the Qur'an doesn't inspire much confidence in this God and his revelations. After all, how do I know that at any time, he isn't currently deceiving me? But taken together with 10:35 which says that God is the one who guides to the truth, that is a contradiction.
Sura 10:35 does NOT say He guides to truth EXCEPT in a few circumstances. "God guides to truth" is an ABSOLUTE statement. And it is wrong, because in 4:157 he does make believe people in something that is false. And the problem is, he mislead also those who want to follow God, not only those who are his enemies anyway. Or how do you explain that the disciples and all of early Christianity believed in the crucifixion?
Allah leads astray whom he pleases,
and he guides whom He pleases, ...
-- Sura 14:4
And how do we know in which of Allah's categories of pleasure we fall? How sure can a Muslim be that he is one of those guided right and not one of those led astray? Indeed how do we know that all of Islam is not the "leading astray" category and Christianity is the right one?
A Muslim response
Contradictions in the Qur'an
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