Parshat Shoftim

Devarim 18:13
You must be wholehearted (tamim) with the LORD your God.
walk before him wholeheartedly, put your hope in Him and do not attempt to investigate the future, but whatever it may be that comes upon you accept it wholeheartedly, and then you shall be with Him and become his portion.
[on Bereshit 25:27, where Jacob is referred to as an ish tam]: ish tam: One who is not ingenious in deceiving people is called tam — plain, simple.
Kitzur Baal Haturim (Jacob ben Asher, Toledo, Spain, 1300)
Wholehearted: The letter ‘Tav’ is large, indicating that if you go whole heartedly, it is as if you have fulfilled from Aleph to Tav.
Psalm 131
O LORD, my heart is not proud nor my look haughty; I do not aspire to great things or to what is beyond me; But I have taught myself to be contented like a weaned child with its mother; like a weaned child am I in my mind.
Rabbi Adin Steinsaltz
… the letter tav … is traditionally written in Torah scrolls larger than the other letters of the word [tamim]. Rabbi Naftali of Ropshitz … once said that the reason for the large tav is so that there should be room inside it for everyone, so that no should considered himself too big and great to fit into this wholeheartedness.
In modern Hebrew, a tamim is a naif, a person whose mental capacities may be lacking in some way. … [But] the Torah speaks of temimut in the sense of wholeness and wholeheartedness.
To be wholehearted with God your Lord means to be completely in God’s domain and not to go outside to get a glimpse of the future. As such temimut is truly a simple matter. It is the simplicity of one who lives within a world of wholeheartedness.
Temimut is measured by a person’s initial reaction: Does he immediately block out everything that he encounters, or does he come with the willingness to listen and accept? After the initial acceptance, there is certainly room for investigation and examination, study and search, and sometimes one in fact discovers that the thing in question must be rejected. But one’s initial reaction is what determines if one is tamim or not.
When one loses the ability to see something new and simply go with it — whether because of one’s own personality, the society in which he lives, or the education that he received — this is a poisonous way to live one’s life.  … They lose the simple ability to recognize and accept the good in things. … The problem exists primarily with those who have already encountered dishonesty in interpersonal relationships.
What, then can be done? … Rabbi Shimshon from Kinon used to claim that he prayed with the mentality of a young child, that is to say, with the same temimut or simplicity that a young child has.
Devarim 16:20
Justice, justice shall you pursue.
Rabbi Yehudah Leib
“Justice, justice shall you pursue.” There is no final depth or end to justice and truth; we always have to go deeper, seeking out the truth within truth. 
How do you reconcile simple wholeheartedness with always having to go deeper in the search of truth? Aren’t these contradictory?