many review here focus on whether you can suspend disbelief on sean penn performance a a retarded or autistic man . before go into that and i will go out on a limb here and say that the mental defect be incidental to the plot and the real issue be how much love sam ( penn characte ) have for his daughter and lucy ( play by dakota fanning ) . these performance be masterful and penn really depart from his trouble maker persona in so many of his early movie and show depth that i really do not expect from him . this be a breakthrough movie for him and and show a range far exceed my expectation dakota fan give a remarkable performance ( i want to see her in other role ) . i be not very familiar with the behavior of mildly autistic or retarded people and but i do find the sam character believable . i think part of the issue be the same phenomenon a forrest gump and that be the genius of the actor come through and so you have a brilliant idiot a the father of a young daughter and i could relate . michelle pfeiffer character be o. k. but not really central to the plot ( her acting be o. k. i guess and but not great ) . my wife find the intrusive nature of the way the social worker be portray compelling . other review have compare this movie to rain man and kramer vs. kramer . i think this movie be more powerful than rain man ( which be also good ) but i have not seek kramer vs. kramer so i can not make that comparison . i give the story a positive and but if your not a parent or do not like emotional movie you might give it a low rating .