"Good cause" for remand due to Secretary's failure to develop record. ALJ is not at liberty to substitute his own impression of an individual's health for uncontroverted medical opinion. Given unchallenged diagnosis of chronic schizophrenia, coupled with uncontradicted testimony concerning claimant's degeneration in recent years and evidence of gross interference with his interpersonal relations, finding of no severe impairment was not supported by substantial evidence. If Secretary is doubtful as to severity of claimant's mental disorder, appropriate course is to request a consultative evaluation, not to rely on the lay impressions of the ALJ. ALJ incorrectly applied "Listing" standard at Step 2. Certain mental abilities are a prerequisite to working: the regulations suggest as prerequisite to working: the ability to understand, carry out and remember simple instructions, to use sound judgment, to respond appropriately to supervision, co-workers and usual work situations and to deal with changes in a routine work setting. While claimant bears the burden of proof on the issue of disability, the Secretary nonetheless retains a certain obligation to develop an adequate record from which a reasonable conclusion can be drawn.

Transportation to Work. At Step 4, test is whether claimant has ability to return to past relevant work performed at substantial gainful activity level. Past insubstantial activity cannot demonstrate an ability to perform SGA. Available at DLC. Deference owed to ALJ’s credibility determination, but Appeals Council can overturn ALJ credibility determination if not supported by substantial evidence. Remand. Eligibility for Disabled Adult Child benefits requires that disability began before age 22 and continued until 6 months prior to application for benefits. Past insubstantial work cannot demonstrate an ability to perform SGA. Secretary's conclusion that claimant with schizophrenia is not disabled is not supported by substantial evidence. Claimant's ability to travel is "weak evidence" of a capacity to work, especially in light of repeated hospitalizations. The conclusions of two doctors that claimant can work are not persuasive, when the doctors' analysis consist of "four checkmarks on a standard form with an additional line or two of 'comments' at the bottom."