The fine point to recognize is here, that we not imagine that there is a contradiction between the two. The fact is that we both accept God’s justice as well as the freedom and responsibility of His servants as well as unity and His rule over the entire universe of existence and this is that very thing which is known as the ‘middle way’ (something which is between two extremes).
Let us clarify this with an example as the issue is a very complicated one. Let us assume that you are traveling on an electric train and you are the driver of the train. A strong electric cable has been placed along the line of the train and the train is connected with a link to this electric cable and moves and moment after moment the electricity is passed to the locomotive in such a way that if for just one moment, the electricity to the locomotive stops, the whole train will stop. Without doubt, you are free. You can stop wherever you want and you can move at your own speed. But in spite of all of this freedom, the person who is sending the electricity can, at any moment, make you stop because all of your power and strength is that very electricity and he holds the key.
When we note this example with care, we see that even though one has such freedom, choice and responsibility, one is completely at the disposal of the power of another and these two do not contradict each other.
Now let us return to the main point. God has given us physical power or strength and from moment to moment, it continues and if it is cut off for even a moment, and our connection with Him be cut off, we would be destroyed. If we can do anything it is because we have strength which He has given us and it continues moment by moment and even our freedom and choice is also from Him. That is, He willed that we be free and by making use of this great Divine kindness, one can transform one’s self.
Thus, at the same time that we have free choice and a free will, we are in His grasp and we will never move beyond His realm. At the same time that we have strength and power, we are dependent upon Him and without Him, we will be destroyed and this is what ‘the middle way’ means because neither have we recognized any creature to be equal to God, which would bring multitheism nor do we believe creatures are obliged to act as they do which would bring oppression.
We have learned this lesson from our pure Imams, peace be upon them. Whenever they were asked, “Does anything exist between fatalism and conferring?” They said, “Yea. More extensive than the distance between heaven and earth.” 1
 See Usul Kafi, vol. l, p. 121
Ref: Fifty Lessons of Principles of Belief for Youths; Ayt. Makarem Shirazi; Translated by: Bahador Shirazian; Published by: Ahlul Bayt World Assembly