The phrase "on the surface" is commonly used to indicate that something appears to be a certain way, but there may be more to it beneath the exterior. Synonyms for this phrase may include "superficially," "at first glance," "externally," or "seemingly." These terms suggest that while something may seem one way from the outside, closer inspection or analysis may reveal deeper truths or hidden complexities. Other options could include "surface-level," "skin-deep," or "apparently," all of which indicate a similar idea that there may be more going on beneath the surface. Choosing the right synonym can help to convey a specific nuance or emphasis in communication.