What do you think is the most controversial idea in our time?

Religion.

gay marriage.

legalizing illegal immigrants.

Does life begin at conception.

Stem cell research, along with everything else that has been mentioned. It’s too hard to pick just one.

Theory of evolution.

genetically modified foods

abortion & “global warming”

Paul is dead

global warming, evolution (still), minding your own business…haha (i included the last one because i think it basically includes gay marriage, religion, abortion, etc)

Mainly issues in the field of bioethics imo – human genetic engineering, cloning, stem cell research, euthanasia and so on… any act that involves interfering with human life, especially the DNA imo.

Not so much one idea but those issues pose very polarizing questions to humanity because of the incredible benefits and dangers of this field.

The separation of church and state.

Who is God? What does God want?

The answers to those two questions seem to me to be the basis of many of the disagreements above, based on religion, church & state, gay marriage, stem cells, abortions, etc.

I agree with trustinglife. These questions are the seeds from which many a war is waged.

That would be why they are so controversial as stated in the original question.

Stem Cell Research
Cloning
AI

Controversial? All aspects of Euthanasia.

Busing. Was it really necessary and why is it still in force in some states today?