EXHIBIT 8.1



                     [Letterhead of Pillsbury Winthrop LLP]


September 20, 2002

Fair, Isaac and Company, Incorporated
200 Smith Ranch Road
San Rafael, California 94903

Ladies and Gentlemen:

We are acting as counsel for Fair, Isaac and Company, Incorporated, a Delaware
corporation ("Fair, Isaac"), in connection with Fair, Isaac's Registration
Statement on Form S-3, combined with the Post-Effective Amendment No. 2 to
Registration Statement of HNC Software Inc., a Delaware corporation and, as of
August 5, 2002, a wholly-owned subsidiary of Fair, Isaac ("HNC"), on Form S-3,
registration number 333-72804 (the "Registration Statement").

We hereby confirm that, subject to the qualifications set forth therein, the
prospectus constituting part of the Registration Statement sets forth our
opinion in the section entitled "Material United States Federal Income Tax
Considerations" as to those matters set forth therein as to which we are
described as rendering an opinion. The foregoing opinion is based upon the
Internal Revenue Code of 1986, as amended, Treasury Regulations (including
Temporary and Proposed Regulations) promulgated thereunder, rulings, official
pronouncements and judicial decisions, all as in effect today and all of which
are subject to change, possibly with retroactive effect, or different
interpretations.

We hereby consent to the filing of this opinion with the Securities and Exchange
Commission as an exhibit to the Registration Statement and to the use of our
name therein. In giving such consent, we do not thereby admit that we are in the
category of persons whose consent is required under Section 7 of the Securities
Act of 1933, as amended.

This opinion is being provided to you solely in connection with the Registration
Statement and may not be relied upon, circulated, quoted or otherwise referred
to for any other purpose.

Very truly yours,



/s/ Pillsbury Winthrop LLP