Is there such a thing as moral neutrality in Catholic thought?

What is a good act

This is a great question especially in the age of moral relativism. The Catholic church, informed by the immensely insightful Thomistic analysis of the human act, teaches that behind every action there are unconscious factors at play, some resulted from vices/virtues influenced by our past acts (good or bad) as well as good desires arising from the good God-given human nature (such as self-preservation and procreation instincts and desires for truth, beauty, love, happiness, etc.). We as rational creatures possess God-given reason that take these natural desires and also the moral laws (embedded in our conscience) into consideration, so we can use it to inform our will to direct our action toward God as acts of love, the ultimate measure (cf Gal 5:23b: "against such things [the fruit of the Spirit, including love], there is no law." ). That is why St. Augustine famously says in one of his sermons: "Love and do what you will."

In the example provided, if our reason evaluates that our desires at a given moment (wanting to eat a bowl of cereal) can be realized in the will toward taking an action (eating a bowl of cereal) that is 1) consistent with love towards God as the ultimate end (i.e. nourishing our body is a proximate end consistent with it) and 2) without violating any moral laws within the circumstances of that moment (i.e. we are not harming ourselves or others), then eating a bowl of cereal at that moment is a good act.

Whether there is an act that is morally neutral?

I think it really comes down to defining what we mean by "neutral":

1. On a certain level, nothing is neutral since our action is either consistent with love or not (as Christians understand them).
2. On another level, there are many choices at a given moment that are consistent with love. For example, given a certain morning in a person's life, taking into account the person's health condition, the person probably does NOT need to eat cereal. It's neutral as to his/her choice of breakfast. So there is a certain neutrality about choosing to eat cereal.

What OT and NT are saying about a good act

I think that is why the Psalms and the Proverbs picture our acts as walking down the path of righteousness as a recipe for happiness cf. Ps 119:34-35,

Give me understanding and I will obey your instructions; I will put them into practice with all my heart. Make me walk along the path of your commands, for that is where my happiness is found,

which in Judaism is the concept of Halakha. The path is NOT too narrow as like a tightrope (where we have to fear that a wrong step will land us off a cliff), but also is NOT too wide that anything goes. It is a wide enough like the path of a well-trodden trail in the park that keeps us safe as long as we are staying on the trail, relatively protected from wild animals or unseen natural dangers.

That sense of neutrality seems well supported in the OT. We Christians who in the New Covenant have the indwelling Holy Spirit have God himself to illumine our reason to guide us in making choices consistent with love (since God is love(!)) and give us the grace of prudence to decide among the several morally neutral choices on which one is better for us. Maybe for something as mundane as the brand of cereal to eat our desire can be given a free rein!

Neutrality within the 12 stages of the human action

If we want to see where exactly the neutrality comes into play in the Thomistic analysis of the human act into 12 stages (using the picture taken from an example of a girl wanting to purchase an iPhone) we can make the following observations:

• Step #1 has to be consistent with the ultimate end (a human being loving God out of our nature). There is NO neutrality here.
• But while in Step #1 there can be multiple proximate ends that are also consistent with our ultimate end. There IS neutrality here.
• Our reason should be employed especially in #5 and #7 to back out of the decision to eat cereal, maybe we are about to go to communion (better fast), or we are diabetic and this is our 2nd bowl and it's Fruit Loop / Frosted flakes. Neutrality may not be neutral anymore given the circumstances.
• Our desires can also be consulted and honored in various stages in #2, #4,#8, #10, and especially #12 as we move further along in the decision process, which contributes to our "happiness" as we make and execute the decision. If our desires in all these stages are within the zone of the right path, there is neutrality.
• Our virtues/vices can influence the decision in many of the 12 stages. We should say "no" if eating a bowl of cereal at that moment feeds into a bad habit. Neutrality needs to be informed by what is good for us in the long term.

Responding to the verses you quoted

Regarding Matt 12:30/Luke 11:23, the context is not about a general act, but about who to trust for those who are ambivalent in determining whether Jesus's miracle power came from demon or from God. Jesus's point: all other exorcists contemporaneous with Jesus (Matt 12:27) are "with Jesus" if they believe their power came from God, implying that the Pharisees (in the passage, Matt 12:22-37) are "against Jesus" since they attribute Jesus's power to the devil.

My response: You said "It seems that by saying this, Christ reveals that the Lord accepts no human act that is ordered towards His glory." Anything consistent with love for God is the same with our acts being "ordered towards His glory".

Revelation 3:16 is about the Laodicean church's lukewarmness (Rev 3:14-22) caused by their comfort and riches blinding them to their spiritual poverty (v. 17). The implied sin is that of being indifferent to those who could have used their help (i.e. the "widow and orphans", which in modern times, the persecuted, the crime victims, and the helpless around us). Out of "tough love" Jesus invited them to allow Him to "correct and discipline" them (v. 19) so they have passion to love others more (and by extension, love Jesus more, since any goodwill done to them are done to Jesus, cf. Matt 25:37-40).

My response: This verse is applicable more on the cumulative effects of single decisions that shape life in a certain direction rather than about each individual decision (like eating cereal). Direction of life is certainly NOT neutral, as in Judgment Day Jesus evaluates our whole life. We need prudence so that our individual morally neutral action does not accumulate in a certain orientation towards the world, which could have resulted in lukewarmness that could have degenerated into apostasy in loving the world more than loving Jesus. So this verse is about the role of virtue/vice as effect of an individual morally neutral act.