speculate
definition
to believe something especially on uncertain grounds
example
Some early philosophers speculated that curiosity was an instinct that helped humans adapt to new environments by driving them to explore.
synonyms
theorizehypothesize
word origin — late 16th century: from Latin speculat- ‘observed from a vantage point’, from the verb speculari, from specula ‘watchtower’, from specere ‘to look’