We have interpreted the presumption under section 411.6(5) in a number of cases. Most illustrative are two cases cited by the district court Riesner v. Board of Trustees of the Fire Retirement System of Dubuque, 203 N.W.2d 812 (Iowa 1973), and Benson v. Fort Dodge Police Pension Board of Trustees, 312 N.W.2d 548 (Iowa 1981). In Reisner we explain the officer's burden is only to show existence of the disease, not that it "was incurred in or aggravated by the actual performance of duty at some definite time and place. . . ."

The fact that a different or opposite result may have been fully justified by the record is of no importance. A trial de novo is not ordinarily permitted on certiorari. See Reisner v. Board of Trustees of Fire Retirement Sys., 203 N.W.2d 812, 814 (Iowa 1973); Cedar Rapids Steel Transp. v. Iowa State Com. Com'n., 160 N.W.2d 825, 831 (Iowa 1968), cert. den., 394 U.S. 918, 89 S.Ct. 1189, 22 L.Ed.2d 451 (1969). See also Collier v. Denato, 247 N.W.2d 236, 237-239 (Iowa 1976); State v. Cullison, 227 N.W.2d 121, 126-127 (Iowa 1975).

First, the applicant must suffer from an injury or disease incurred in or aggravated by the actual performance of duty at some definite time and place. Second, the applicant must be totally and permanently incapacitated for duty as a natural and proximate result of the injury or disease. Reisner v. Bd. of Trustees, 203 N.W.2d 812, 814 (Iowa 1973). A "disease" under the statute is limited to the heart, lungs, or respiratory tract.

We also remember that in a substantial-evidence review, "[t]he fact that others may have reached a different conclusion or that an opposite result would have been fully justified by the evidence is of no importance." Vohs v. Dist. Comm'rs , 218 N.W.2d 595, 596 (Iowa 1974) (en banc) (quoting Reisner v. Bd. of Trs. of Fire Ret. Sys. , 203 N.W.2d 812, 814 (Iowa 1973) (en banc)). Patterson also points out that Tidwell received $6,000 from the attorney general's office.

The possibility of drawing two inconsistent conclusions from the same evidence does not prevent an agency's finding from being supported by substantial evidence. Reisner v. Bd. of Trustees of Fire Retirement Sys., 203 N.W.2d 812, 814 (Iowa 1973). As we said in City of Davenport v. PERB, 264 N.W.2d 307, 312 (Iowa 1978), the wisdom of this carefully circumscribed standard of review is demonstrated by the kind of problem involved in the present case.

Significantly, several courts have relied on the fact that the claimant in a particular case had not suffered a reduction in pay or a loss of seniority and rank as a result of being placed on light duty. See, e.g., Winslow, 34 Cal.3d 66, 192 Cal.Rptr. at 632, 665 P.2d at 4; Stuessel, 141 Cal.App.3d at 1054, 190 Cal.Rptr. 773; Hubbard, 150 Colo. at 498, 374 P.2d 492; Michaw, 265 Ind. at 464, 269 N.E.2d 533; Ring v. Langdon, 69 A.D.2d 998, 999, 416 N.Y.S.2d 137 (1979). In contrast, some courts have determined that a police officer or firefighter who is able to perform some, but not all, of the duties of his job classification is incapacitated. See, e.g., Butler v. Pension Bd. of the Police Dep't, 259 Iowa 1028, 1033-34, 147 N.W.2d 27 (1966) (distinguished in Reisner v. Board of Trustees, 203 N.W.2d 812, 815 (Iowa 1973)); Knight v. Board of Trustees, 269 S.C. 671, 679, 239 S.E.2d 720, 723 (1977). The primary rationale of these courts is that the pension statutes are remedial in nature, having been enacted for the benefit of the employee-claimant.

Statutory construction is not a fact question which requires deference. It is not, for example, a question similar to whether a fireman has become physically incapacitated. See Reisner v. Board of Trustees, 203 N.W.2d 812 (Iowa 1973). See also Staads v. Board of Trustees, 159 N.W.2d 485 (Iowa 1968).

While the substantiality of evidence must take into account whatever in the record fairly detracts from its weight, Universal Camera Corp. v. NLRB, 340 U.S. 474, 488, 71 S.Ct. 456, 464, 95 L.Ed. 456, 467 (1951); Briggs, 282 N.W.2d at 743, the possibility of drawing two inconsistent conclusions from the evidence does not prevent an administrative agency's finding from being supported by substantial evidence. Briggs, id.; City of Davenport v. PERB, 264 N.W.2d 307, 311 (Iowa 1978); Reisner v. Board of Trustees of Fire Retirement System, 203 N.W.2d 812, 814 (Iowa 1973). The question is not whether there is sufficient evidence to warrant a decision the agency did not make, but rather whether there is substantial evidence to warrant the decision it did make. Woods, 315 N.W.2d at 841; see Deaver v. Armstrong Rubber Co., 170 N.W.2d 455, 464 (Iowa 1969).

Moreover, it has added a conclusive presumption that those diseases are job related. See Reisner v. Board of Trustees, 203 N.W.2d 812, 814-15 (Iowa 1973). Because the definition is exclusive, plaintiff was entitled to accidental disability retirement only if he established as a matter of law that he had a disease within the definition.

The possibility that two inconsistent inferences may reasonably be drawn from the evidence does not itself deprive findings of substantial evidentiary support. Ellis v. Iowa Department of Job Service, 285 N.W.2d 153, 156 (Iowa 1979); Briggs v. Board of Directors, 282 N.W.2d 740, 743 (Iowa 1979); City of Davenport, 264 N.W.2d at 312; State ex rel. Iowa Employment Security Commission v. Iowa Merit Employment Commission, 231 N.W.2d 854, 858 (Iowa 1975); Reisner v. Board of Trustees, 203 N.W.2d 812, 814 (Iowa 1973). Courts do not hear these cases de novo.