Is Tim Keller's view of idolatry Biblical? I just finished reading Tim Keller's Every Good Endeavor. In it, he says that in Ezekiel, there is a part where it talks about idols within the heart, "which involves making good things into ultimate things". Also, in one of his sermons, he brought up the fact that Martin Luther says that the 1st commandment underlies all the other commandments, since not putting God first and foremost (even above the good things in life) is what causes one to lie, cheat, steal, etc. 

I would like to know if this view of "idolatry" is Biblical (since I read some opposing views somewhere else). If so, could you please provide me with relevant verses from the Bible. 

For my part, I can see what Keller/Luther are getting at, and it seems to agree, somewhat, with Paul's assessment that whatever is not from faith is sin. However, it seems to downplay the seriousness of sin as something violating God's Law.
It is not for us to Judge either preacher, that is reserved for Jesus:

John 5:22 and 23  For the Father judgeth no man, but hath committed all judgment unto the Son: That all men should honour the Son, even as they honour the Father. He that honoureth not the Son honoureth not the Father which hath sent him.

That having been said; We can take a look at Scripture to see what they have to say regarding this.

Matthew 22:37 through 40  Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. 38  This is the first and great commandment. 39  And the second is like unto it, Thou shalt love thy neighbour as thyself. 40  On these two commandments hang all the law and the prophets.

What Jesus appears to be pointing out here is that if you do not do these two things, then it will be almost impossible to keep the rest of the Law.
So Let's see what other Scriptures may help in understanding this; although many questions that arise in life are not directly addressed in Scriptures we are given clues as to how to handle them.

Matthew 5:21 and 22  Ye have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: 22  But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.
Matthew 5:27 and 28  Ye have heard that it was said by them of old time, Thou shalt not commit adultery: 28  But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.

From these two Scriptures Jesus is teaching us two things:

It is our precepts that determine our compliance with the Commandments, and not our actions, as is expressed in the fact that although we may not actually kill someone, it is the desire to do so that is not in compliance. After all how can you love your neighbor as yourself if stay mad at him, and especially if it is only you who have perceived wrong doing by him.

If we desire to do wrong it is tantamount to having done it. Even though we may contemplate stealing someone else's wealth for our own use, we have in effect not only put our greed above the other person's welfare; but we have denied God's promise to supply all of our needs as Jesus explained in his sermon on the Mount.



Mat 5:3 through 11  Blessed are the poor in spirit: for theirs is the kingdom of heaven. 4  Blessed are they that mourn: for they shall be comforted. 5  Blessed are the meek: for they shall inherit the earth. 6  Blessed are they which do hunger and thirst after righteousness: for they shall be filled. 7  Blessed are the merciful: for they shall obtain mercy. 8  Blessed are the pure in heart: for they shall see God. 9  Blessed are the peacemakers: for they shall be called the children of God. 10  Blessed are they which are persecuted for righteousness' sake: for theirs is the kingdom of heaven. 11  Blessed are ye, when men shall revile you, and persecute you, and shall say all manner of evil against you falsely, for my sake.

Jesus is here saying that God will provide all of our heart's desires as long as those desires are in keeping with serving him. And:

Matthew 6:8  Be not ye therefore like unto them: for your Father knoweth what things ye have need of, before ye ask him.

If there is one common concept in these Scriptures it is that God knows and considers our intents and our innermost desires. And that it is those upon which compliance with the Commandments is judged. And because Jesus has been tempted in every way in which we can be tempted which would have to include disobedience of every one of the Commandments, he alone is qualified to judge.
So let's take a look at  Chapter 14 of Romans and see if we can more discern what Paul is conveying.
Let's take a look at this excerpt from John Gill's commentary of the whole Bible.

for whatsoever is not of faith is sin. This is a general rule, or axiom, which is not only applicable to the present case, but to any other, whether of a natural, civil, moral, or evangelic kind: &quot;whatsoever does not spring from faith&quot;, as the Arabic version renders it, cannot be excused of sin; whatever is not agreeable to the word and doctrine of faith, ought not to be done; whatever is done without faith, or not in the exercise of it, is culpable, for without faith nothing can be pleasing to God; and whatever is contrary to the persuasion of a man's own mind, is so far criminal, as it is a violation of his conscience; whatever men do, especially in a religious way, they ought to make faith of it, or to be fully persuaded of it in their own minds, or they act amiss:

It appears from this commentary that our purpose for anything we do should be based in our desire to please God, which is an integral part of Worship so it is up to you to decide whether or not mental disobedience of the command to have no other gods before me; is or is not is included. For my part I am inclined to believe it is based on the Scriptures I have quoted.
Hope this helps.