speculate

to believe especially on uncertain or tentative grounds

• “Scientists supposed that large dinosaurs lived in swamps”

talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion

• “We were speculating whether the President had to resign after the scandal”

reflect deeply on a subject

• “I mulled over the events of the afternoon”
• “philosophers have speculated on the question of God for thousands of years”
• “The scientist must stop to observe and start to excogitate”

invest at a risk

• “I bought this house not because I want to live in it but to sell it later at a good price, so I am speculating”