Before revision: Political similarity One general criticism motivating research of different explanations is that actually the theory cannot claim that "democracy causes peace", because the evidence for democracies being, in general, more peaceful is very slight or nonexistent; it only can support the claim that "joint democracy causes peace".
After revision: Democracy differences One general criticism motivating research of different explanations is that actually the theory cannot claim that "democracy causes peace", because the evidence for democracies being, in general, more peaceful is very slight or nonexistent; it only can support the claim that "joint democracy causes peace".