Most of us understand that the phrase “No creed but Christ” is very unhelpful for two reasons: 1) it is illogical because it is creed in and of itself, and 2) one has to define “Christ,” and in so doing, the result will be something like a creedal statement. Geerhardus Vos tackled this unhelpful anti-creedal attitude which was evidently around 100 years ago:
“Faith presupposes knowledge, because it needs a mental complex, person or thing, to be occupied about. Therefore, the whole modern idea of preaching Jesus, but preaching him without a creed, is not only theologically, not merely scripturally, but psychologically impossible in itself.”
“The very names by means of which Jesus would have to be presented to people are nuclei of creed and doctrine. If it were possible to eliminate this, the message would turn to pure magic, but even the magic requires some name-sound and cannot be wholly described as preaching without a creed. The vogue which this programme has acquired is to some extent due to the unfortunate, and altogether undeserved, flavor clinging to the term ‘creed,’ as though this necessarily meant a minutely worked out theological structure of belief. That is not meant, but belief there must be before faith can begin to function, and belief includes knowledge [Matt. 8.10, Lk. 7.9]. This knowledge may have been gathered gradually, almost imperceptibly, from countless impressions received during a brief or longer period of time, but epistemologically it does not differ from any other kind of mental act however acquired. To be sure, mere knowledge is not equivalent to full-orbed faith, it must develop into trust, before it is entitled to that name.”
For more on this from Vos, see the context of page 389 in Biblical Theology: Old and New Testaments.