 The vera causa ideal may also have been effective in the historical episodes presented in previous sections. In the oxidative phosphorylation case, the hypothetical chemical intermediate was never accepted because biochemists failed to isolate and detect it. Mitchell’s chemi-osmotic gradient, by contrast, was readily accepted. However, it’s causal efficacy in powering phosphorylation was doubted. This is where the Racker-Stoeckenius came in: By demonstrating this causal efficacy, it completed the case for chemiosmotic coupling in compliance with the vera causa ideal.