How did Justice Stephen Breyer criticize the historical reasoning in District of Columbia v. Heller?

In his dissenting opinion in McDonald v. City of Chicago (2010), Justice Stephen Breyer criticized the historical reasoning employed by the majority in District of Columbia v. Heller (2008) as being flawed.1

Breyer argued that the historical evidence regarding the fundamental nature of a private right to armed self-defense was, at best, unclear. Because he viewed the historical analysis in Heller as insufficient, he contended that the question of whether the Second Amendment should be incorporated against the states must instead be decided based on other factors. These factors included:1

• The ascertainable motivations of the Constitution’s framers.1
• Whether there is a contemporary consensus that the right is fundamental.1
• Whether enforcing the right against the states would further the broader objectives of the Constitution, such as maintaining a democratic government, fostering equal respect for individuals, and ensuring well-functioning institutions based on the separation of powers.1

Breyer concluded that when these factors are properly considered, they weigh against the incorporation of the Second Amendment.1