Definition of "speculator"

a bold and paradoxical speculator

c. 1683, Thomas Browne, Certain Miscellany Tracts

[…] in things of Fact, the People are as much to be believed, as the most subtle Philosophers and Speculators, since here sense is the Judge.

1666, Joseph Glanvill, Philosophical Considerations concerning Witches and Witchcraft

For, in the earlier part of the seventeenth century, a speculator who had dared to affirm that the human soul is by its nature mortal, and does, in the great majority of cases, actually die with the body, would have been burned alive in Smithfield.

1848, Thomas Babington Macaulay, The History of England from the Accession of James the Second