Solaris
The planet and the mega-organism are both called Solaris and both are symbolic of the vast gulf between what man knows and what he does not. The more they find out about Solaris, the less they understand. The more attempts the planet-organism makes to communicate with them, the more unnerved the crew becomes.
The Visitors
The Visitors are artificial beings created by the ocean-organism Solaris from the exploratory team’s memories, fears, and fantasies; as such they are symbolic of precisely that—memories, fears, and fantasies. The first documented encounter of Kris with these strange beings is with the larger-than-life id-clone created from Snow’s thoughts. She/It is of particular importance to the novel as she/it is the embodiment of an allusion that the author is trying to draw between the exploration of Solaris and previous historical explorations; that is to say that science fiction is a mere variant of exploration stories of bold pioneers going off to parts unknown for glory and fame—often at the cost of the indigenous population, or worse, to enact genocide to exploit natural resources and to conquer land.
Mimoids
The mimoids are structures created by the Solaris ocean-organism that look like objects or images familiar to the crew members. Similar to The Visitors, mimoids are theorized to be prototypes of the Visitors, similarly copied from human thoughts. In that same regard mimics are symbolic of dreams and may be understood as the planet-organism’s analogue for human writing and symbolic of its attempt to communicate with the humans exploring it.
Books
Books are symbolic of humanity’s ultimately futile attempt to explain the unexplainable and contain the vast sum of knowledge that they come across. Kris reads a lot of books while on duty and he fills out many entries in the books of data recordings he makes while staying on Solaris, all of it done in great, painstaking detail. All his learnings, however, eventually turn out to be completely pointless, as The Visitors and Solaris keep throwing new surprises his way, nullifying his previous notations about the phenomena he had just documented.
Tools
Kris finds a box full of mangled tools early in the novel. The tools, by his description, are supposed to be nigh-indestructible so not only does he wonder at how they came to look like that but he is also genuinely puzzled by who or what did it and why they’d—whoever “they” may be—would go to such lengths to ruin these tools. These useless tools, like the books filled with scientific babble, are symbolic of the futility of the explorers endeavors. The planet-organism is indeed intelligent; its intelligence however is either too vast for standard human understanding or worse—having been developed under a completely different set of circumstances, it may be too different, too alien for the human mind to comprehend in any useful capacity.
