Piety or Knowledge?

I have written before of the battle between holiness and justice.  Some say we are to focus on our own moral purity, on becoming more like Jesus.  Others say we are to focus on social justice for others, on being Jesus to those around the world.
Holiness
Justice
When describing the wickedness of Israel, Isaiah says “He looked for justice, but saw bloodshed; for righteousness, but heard cries of distress.”
It seems that one of the Deceiver’s favorite ploys is to take a set of discipleship practices, a pairing that works best when done in concert with each other, and separate them, throwing them into battle with each another.  In doing so, he not only diminishes the efficacy of both practices but he also divides the very body of Christ.
Clearly both holiness and justice are important.  We should not focus on half of God’s commands to the exclusion of the rest.
Another battle I’ve been trying to understand is the battle between piety and knowledge.
Is it better to obey God, to act on His behalf, or is it better to learn about God, to know what it is He commands?
piety
knowledge
Some would say that knowledge is too dry, that the life of the mind is on par with selfishness.  It brings to mind ivory towers and keeping oneself unsullied by the realities of the real world.
While it is true that focusing solely on knowledge and learning would keep one from ever actually helping this world of hurting people, modern church culture seems to lean too heavily in the direction of anti-intellectualism.  There is a growing spirit of pragmatism in our churches.  A spirit whose first question about an idea is not “Is it true?” but “Does it work?”.
“Young people tend to be activists, dedicated supporters of a cause, though without always inquiring too closely either whether their cause is a good end to pursue or whether this action is the best means by which to pursue it.” ~ Rev. John R. W. Stott in an address at the Inter-Varsity Fellowship Annual Conference
It seems this is another set of discipleship practices that when separated leads to reduced success.
On one hand you have people rushing crazily about for the next good idea regardless of the wisdom or truth of it, perhaps even causing more harm than good.  On the other hand you have people sitting stagnant with their books, not allowing any of the knowledge of God to seep into their hearts and affect the world around them.
Both piety and knowledge are desperately needed together.  Only with knowledge can you know what God truly wants, what is the wise action to take.  Only with piety can your own heart be changed, can the hearts and lives of other people be changed.
Paul says in II Corinthians that we are to take every thought captive toward the obedience of Christ.
Piety and knowledge.  Obedience and intellect.  The heart and the mind.
Both are needed.  Both are required to continue to bring about God’s kingdom here on earth.
Only together can these practices nourish “a warm and fruitful devotion set on fire by truth.” (Stott)