Keynes's economic thinking only began to achieve close to universal acceptance in the last few years of his life. On a personal level Keynes's charm was such he was generally well received wherever he went – even those who found themselves on the wrong side of his occasionally sharp tongue rarely bore a grudge. Keynes's speech at the closing of the Bretton Woods negotiations was received with a lasting standing ovation, rare in international relations, as delegates acknowledged the scale of his achievements made despite poor health.

Austrian School economist Friedrich Hayek was Keynes's most prominent contemporary critic, with sharply opposing views on the economy. Yet after Keynes death he wrote:

Lionel Robbins a former Austrian School economist who had suffered many heated debates with Keynes in the 1930s, had this to say after observing Keynes in early negotiations with the Americans while drawing up plans for Bretton Woods:

Douglas LePenn, an official from the Canadian High Commission , wrote:

Bertrand Russell named Keynes one of the most intelligent people he had ever known, commenting:

Keynes' obituary in The Times included the comment:

As a man of the centre described as undoubtedly having the greatest impact of any 20th century economist, Keynes attracted considerable criticism from both sides of the political spectrum. In the 1920s, Keynes was seen as anti establishment and was mainly attacked from the right. In the "red 1930s" many young economists favoured Marxist views even in Cambridge, and while Keynes was engaging principally with the right to try to persuade them of the merits of more progressive policy, the most vociferous criticism against him came from the left who saw him as a supporter of capitalism. From the 1950s and onwards most of the attacks against Keynes have again been from the right.

In 1931 Friedrich von Hayek extensively critiqued Keynes's 1930 Treatise on Money, only to have Keynes assert that the Treatise no longer reflected his thinking. However, after reading Hayek's The Road to Serfdom , Keynes wrote to Hayek saying: "In my opinion it is a grand book ... Morally and philosophically I find myself in agreement with virtually the whole of it: and not only in agreement with it, but in deeply moved agreement." Yet he concluded the same letter with the recommendation:

On the pressing issue of the time, whether deficit spending could lift a country from depression, Keynes replied to Hayek's criticism in the following way: