I am trying to find a short story
"Second Dawn", a novelette by Arthur C. Clarke, also the answer to the old questions "Which 70s/80s story/book has horses as protagonists?" and "Short story about alien military telepathy?" and "Short story about a highly intelligent species without any technology". It was first published in Science Fiction Quarterly, August 1951, which is available at the Internet Archive (click here for download options).
involving an alien race of 'Intellectuals.' They possess no opposable thumbs or other limbs to control their world.
Both the Atheleni and their cousins, the Mithraneans, possessed mental powers that had enabled them to develop a very advanced mathematics and philosophy: but over the physical world they had no control at all. Houses, tools, clothes—indeed, artifacts of any kind—were utterly unknown to them. To races which possessed hands, tentacles, or other means of manipulation, their culture would have seemed incredibly limited: yet such is the adaptability of the mind, and the power of the commonplace, that they seldom realized their handicaps and could imagine no other way of life. It was natural to wander in great herds over the fertile plains, pausing where food was plentiful and moving on again when it was exhausted. This nomadic life had given them enough leisure for philosophy and even for certain arts. Their telepathic powers had not yet robbed them of their voices and they had developed a complex vocal music and an even more complex choreography. But they took the greatest pride of all in the range of their thoughts: for thousands of generations they had sent their minds roving through the misty infinities of metaphysics. Of physics, and indeed of all the sciences of matter, they knew nothing—not even that they existed.
I think the basis of the story is their discovery of a way to influence another unintelligent species that can manipulate objects.
"The solution is, quite literally, in the hands of the Phileni. We must use their skills to reshape our world, and so remove the cause of all our wars. We must go back to the beginning and re-lay the foundations of our culture. It won't be our culture alone, though, for we shall share it with the Phileni. They will be the hands—we the brains. Oh, I have dreamed of the world that may come, ages ahead, when even the marvels you see around you now will be considered childish toys! But not many are philosophers, and I need an argument more substantial than dreams. That final argument I believe I may have found, though I cannot yet be certain.
This leads to a new start for them. They may have been at risk of breeding beyond available resources.
"The mind is a wonderful thing, Eris—but by itself it is helpless in the universe of matter. We know now how to multiply the power of our brains by an enormous factor: we can solve, perhaps, the great problems of mathematics that have baffled us for ages. But neither our unaided minds, nor the group-mind we've now created, can alter in the slightest the one fact that all through history has brought us and the Mithraneans into conflict—the fact that the food supply is fixed, and our populations are not."
The story ends with explorers returning from sea. They may have discovered a new land into which they can expand.
"Land! They've found land—a whole new continent waiting for us!"
The last few scenes have a darker flavor where one character has been presented with a rock that glows in the dark.
Eris strained his eyes into the darkness. At first he could see nothing: then, slowly, a glimmering blue light became faintly visible. It was so vague and diffuse that he could not focus his eyes upon it, and he automatically moved forward.
"I shouldn't go too near," advised Aretenon. "It seems to be a perfectly ordinary mineral, but the Phileni who found it and carried it here got some very strange burns from handling it. Yet it's quite cold to the touch. One day we'll learn its secret: but I don't suppose it's anything at all important."
The author then takes over and makes some comments about most species passing one crossroads only to meet another.
Alone, perhaps, of all the races in the Universe, her people had reached the second crossroads—and had never passed the first. Now they must go along the road that they had missed, and must face the challenge at the end—the challenge from which, this time, they could not escape.
In the darkness, the faint glow of dying atoms burned unwavering in the rock. It would still be burning there, scarcely dimmed, when Jeryl and Eris had been dust for centuries. It would be only a little fainter when the civilization they were building had at last unlocked its secrets.