My wife picked up the phrase from Thomas the Train Engine, who is always eager to be a "really useful engine." She made the observation that the same thing is true of our little boys, especially Justinian as the particular case she had in mind. I think it is true of our little girls, too, but with them it is expressed in different ways.
Little boys do want to be "really useful engines," and so do men. They want to be useful, and they want to be admired and appreciated for being useful. They are keen to figure things out and to fix what is broken, to find solutions and solve problems, and to accomplish good things. They want to be useful, and they are gladly willing to work at it, in order to achieve results.
This can be problematic. Like most everything else in this fallen world, the desire to be "useful" is easily twisted into works righteousness and self-idolatry. Men are prone to define who they are in terms of what they do and accomplish; to measure their worth by their achievements. "Usefulness," then, may have more to do with pridefulness than sacrificial loving service. The male ego is surely one of those false gods and household idols that must be dethroned and broken through daily contrition and repentance.
For all of that, though, there is an inherent goodness in a man's desire to be a "really useful engine." The inclination to help and serve, to fix what is broken, to rectify what is wrong, to be strong for the weak, to work hard for the benefit of others — surely all of this is good and right, and it is put to good use by the Lord through the order of natural law. A lot of good stuff is done for lots of neighbors by men who may be driven by no other motivation than to be "really useful engines." Many wives and children are well served in this body and life because their man wants to be useful. That is even apart from the sanctified law of Christian faith and love.
Our Lord Jesus Himself is a "really useful engine," if it is not too crass a thing to say concerning Him who is our Life, our Light and our Salvation. "My Father is working until now," He says, "and I Myself am working." His "usefulness" does not define or constitute who He is or what He is worth, but derives from His Person as the Son of God, the only-begotten of the Father, full of grace and truth. He does what He does, for us, because of who He is. And men made in His own Image are at their best when they work to serve their neighbor in love; when they are useful, not in order to become what they are not, but to be who they are created to be.
The zeal of little boys to be "really useful engines" needs to be guided and governed by fathers who have learned to be useful in faith and love, as men after God's own heart. They need to be taught the knowledge and skills to be useful; for good intentions and trying hard are not always so helpful. They also need a good example of sacrificial service for love's sake; like father, like son. And young men especially need the consolation and comfort of the Gospel, which never does hinge on their usefulness. For it is only when they know themselves to be sons of God in Christ Jesus that they can truly know the desire to be "really useful engines," not for prideful self-righteousness, but gladly, for the sake of their Father in heaven and their neighbor on earth.
I've been pondering how it may be similar and different for little girls, young ladies and women. I don't doubt that women also want to be "really useful," but I have a sense that such a desire may take a very different form with them. Women seem less inclined than men to define who they are and what they are worth in terms of their abilities and achievements. Perhaps they interpret their "usefulness" more in terms of their relationships: in the giving and receiving of love, in nurturing and caring, in listening and speaking. Am I missing the mark? A little help, anyone?
What isn't different for girls and boys, men and women, is that "usefulness" is best exercised in faith and love, and that human identity and real worth are not achieved by "usefulness" of any sort, but are bestowed by the grace of God in Christ Jesus our Lord.