D​‌‍‍‍‌‍‍‍‌‍‍‍‌‌‌‌‌‌‍‍​escribe Beck’s cognitive model, how it has evolved over time and critic​‌‍‍‍‌‍‍‍‌‍‍‍‌‌‌‌‌‌‍‍​ally evaluate it as a theory of depression in light of modern evidence​‌‍‍‍‌‍‍‍‌‍‍‍‌‌‌‌‌‌‍‍​.