Maybe I am misunderstanding this point entirely, and feel free to correct me if this is the case. However, since we are pursuing knowledge, which must come from inquiry, which must first come from a proposal, I would like to propose that there is, in fact, a middle ground. And more than that, there is always a middle ground.
Let me begin by saying that I am not a philosopher. I am an engineer. I am used to dealing with problems and finding a solution. Note that I did not say the solution. For as I am beginning to slowly grasp, in engineering there are often multiple solutions that are workable and practical to any problem.
Apply this idea to our actions. Is any one action a singular solution or a singular result of a separate action? I would argue no. However, it is the only course of action taken. But what drives this action? What motives, besides our "separate action", lie behind our one singular course of action taken? This is where it gets tricky.
Our actions are partially tainted. Even the most generous man may hold pride in his heart for the amount he has given away. But how do we prove this? The easiest way to prove sinfulness is to examine our own lives. I think back to all of my "good" deeds, only to find that behind them lies a prideful, or resentful, or reluctant heart. Our hearts, being polluted and perverted by sin, do not have the power to motivate us to do otherwise. Even when we attempt holiness, we still have upon us the taint of sin, like a stain that cannot be removed. This is dreary, burdensome stuff. But in order to understand why there must be a middle ground, we must understand our own sin.
Here lie the final questions: Is an action that is tainted by this stain of sin still "sacred"? Or should it be considered purely "secular"? If all actions tainted and stained by sin are "secular", there would be no goodness, no grace within this world. Already, we can see the falseness of this idea. There is in this world a presence of goodness which can be accredited to God and the Holy Spirit, and some actions reflect, at least partially, this glory. Then let us examine the other question; the question of a tainted action's sacredness. To be sacred is "to be holy and set apart by God." How can an action motivated by a bundle of good and bad intentions be considered holy and sacred? God is perfect. An action affected by sin is not perfect because of the destruction polluting effect that sin has on everything. Therefore, there must be an answer that allows an action to be simultaneously "sacred" and "secular." This is what I am calling the middle ground.
In this middle ground, actions can be partially sacred, but never fully.
I am not saying, however, that actions are devoid of meaning. There is a meaning attached to all actions, thoughts, and decisions. Aside from anecdote, this is difficult to prove. It is difficult to see how that one sheet of paper I throw away could change a different person's life. What is remarkable is the fact that our God can use small, "insignificant" actions to change other lives. The meaning of actions can also be considered in a different light. Since sin and goodness seem so wrapped together, how can an action have neither? How can the taint of sin not affect everything we do once we accept its pervasiveness? And how can we not see the holiness and goodness that must come in some way with the action?