What follows is not intended to vindicate constructivist accounts of the natural sciences but rather to encourage a better understanding of what they involve. I begin by emphasising that there are many different versions of constructivism and that few extant criticisms apply to all of them. Even so, practically all versions of constructivism reject strong realist accounts of the nature of scientific concepts and theories, and I offer an argument in support of this. Consider the many theories once accepted by scientists and natural philosophers but subsequently reckoned to be false and discarded. Surely, a constructivist account of these is uncontroversially preferable to a realist one, wherein the discarded concepts referred to entities that really existed in the external world. Yet realist philosophers have not so far produced any convincing account of how those theories and concepts currently accepted as true differ from discarded ones that were formerly so accepted. Finally, I turn specifically to radical social constructivism, arguably the most uncompromising and intensely criticised of all versions, wherein physical reality itself is alleged to be a construct. Not being an idealist, I offer no defence of this position. I do, however, insist that it not be lightly dismissed, and conjecture that some of the intemperate hostility it elicits is actually a consequence of how difficult it is to find convincing arguments with which to oppose it.