William Rothenstein, a noted British painter, was in Berlin doing a portrait of Einstein. The mathematician was always accompanied to the studio by a solemn, academic looking individual, who sat in a corner throughout the sittings. Einstein, not wishing to waste any time, was putting forth certain tentative theories, to which the silent companion replied only by an occasional nod or shake of the head. When the work was concluded, Rothenstein, who was curious, asked Einstein who his companion was.
“That is my mathematician,” said Einstein, “who examines problems which I put before him and checks their validity. You see, I am not myself a good mathematician.”
Einstein relied more on practical instinct and native genius than on mathematical excellence in making his discoveries.
著名英國畫家威廉．羅森斯坦曾到柏林，為愛因斯坦畫像。這位數學家每次來畫室，總有一人同行，其人表情嚴肅，一副學者模樣，羅森斯坦揮毫時，他就坐在一角。珍惜時間的愛因斯坦，會提出一些還待驗證的理論，而他那個沉默寡言的同伴，則會偶然點點頭或搖搖頭作答。肖像畫好之後，羅森斯坦忍不住好奇心，問愛因斯坦那人是誰。
愛因斯坦說：「他是我的計算師，會檢驗我提出的問題，看看可不可行。我自己並不擅長數學。」
愛因斯坦多所發明，這與其說是憑數學才華，不如說是憑務實的本能以及天生的智慧。