I shall endeavour still further to prosecute this inquiry an inquiry I trust not merely speculative but of sufficient moment to inspire the pleasing hope of its becoming essentially beneficial to mankind.

Evolution is a bankrupt speculative philosophy not a scientific fact. Only a spiritually bankrupt society could ever believe it. Only atheists could accept this Satanic theory.

We have failed to protect science against speculative extensions of nature continuing to assign physical and mathematical properties to hypothetical entities beyond what is observable in nature.

True science is never speculative it employs hypotheses as suggesting points for inquiry but it never adopts the hypotheses as though they were demonstrated propositions.

All the interests of my reason speculative as well as practical combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?

I fear that in the end the famous debate among materialists idealists and dualists amounts to a merely verbal dispute that is more a matter for the linguist than for the speculative philosopher.

He was a dreamer a thinker a speculative philosopher... or as his wife would have it an idiot.