No matter how conscientious they are, historians always have biases that affect their work.
Evidence
No matter how conscientious they are, historians always have biases that affect their work.
Conclusion
Rather than trying to interpret historical events, historians should instead interpret what the people who participated in historical events thought about those events.
Evaluate
The problem with this argument is that the historians are interpreting in both cases. So if they’re likely to bias is likely to affect their interpretation of historical events, it’s also likely to affect their interpretation of what the people who participated in historical events thought about those events as well.