dissenting.
I dissent. I believe that the majority has overstepped its bounds and usurped the jury’s factfinding function by vacating its verdict on damages. It does so by a selective and, I believe, misleading statement of the facts. The following summary, taken from Superior Court’s opinion, more fully and accurately sets out the evidence on which the court gave the instruction at issue and the jury gave its verdict.
“Six physicians testified at length regarding appellant’s condition. In addition to Dr. Koenig, Jerome F. Wiot, M.D., a radiologist, Murray Sachs, M.D., a pulmonary specialist, and David Laman, M.D., also a pulmonary specialist, testified on appellant’s behalf. Morris Zachary Gardner, M.D., a radiologist, and John G. Shively, M.D., a pulmonary specialist, testified on behalf of appellees. Their testimony on the question of the causes of appellant’s disability may be summarized as follows.
*388“Dr. Sachs, Dr. Wiot and Dr. Laman agreed that appellant suffered from pulmonary disease having both obstructive and restrictive components. See, e.g., N.T. Vol. II-A at 10; N.T. Vol. I-A at 764-65. Dr. Wiot explained that with an obstructive lung disease, the airway passages in the lungs are blocked. Id. at 724. Dr. Sachs explained that with a restrictive lung disease, the lungs do not fill to capacity____ Id. at 768.
“Testimony of appellant’s witnesses established that asbestosis is primarily a restrictive lung disease, id. at 769-70 (Sachs); 726 (Wiot), and that emphysema and chronic bronchitis, primarily caused by cigarette smoking, id., are obstructive lung diseases. Dr. Laman stated, however, that while cigarette smoking is a substantial factor in the development of obstructive lung disease, asbestosis has an obstructive component as well, for when asbestos fibers become deposited in small airways in the lungs the air passages become blocked. N.T. Vol. II-A at 16.
“Dr. Wiot, whom appellant had retained to examine his chest x-rays, but who had not otherwise examined appellant, described his findings at trial with the use of the x-rays. He observed ‘emphysematous changes’ and ‘bullous changes’ in the upper portion of the lungs. N.T. Vol. I-A at 667. He explained that bullous changes represent a breakdown in pulmonary tissue and are indicative of emphysema. Id. at 693-94. See also id. at 776-77 (testimony of Dr. Sachs). Dr. Wiot also stated that the x-rays showed ‘long-standing obstructive lung disease.’ Id. Dr. Laman testified that it is not uncommon for cigarette smokers to develop bullae. N.T. Vol. II-A at 23. See also N.T. Vol. I-A at 694 (Wiot). Dr. Wiot and Dr. Sachs agreed that appellant has emphysema. N.T. Vol. I-A at 694, 776-77.
“In further reviewing appellant’s x-rays at trial, Dr. Wiot observed pleural plaques from the mid-zones of the lungs down. Id. at 669-70. Dr. Laman and Dr. Sachs likewise found pleural plaques in the lower two-thirds of the lung field. N.T. Vol. II-A at 12; Vol. I-A at 749. Dr. Wiot, Dr. Sachs and Dr. Laman agreed that pleural plaques are *389caused by inhalation of asbestos fibers. Id. at 697-98, 769-70; Vol. II-A at 13-14. Dr. Wiot described the system used to classify pleural plaques by the density of the opacity and by the number of opacities present in the lungs. Although he described the opacities found in appellant’s lungs as small and irregular, he noted that the size of the opacity bears little relationship to the extent of disability that a person has suffered. N.T. I-A at 667, 683-84.
“Testifying for appellees, Dr. Shively stated that appellant’s chest x-rays showed one pleural plaque consistent with asbestos and that pulmonary function studies that he had conducted of appellant revealed a restrictive lung problem. N.T. Vol. IV at 106-10. Dr. Gardner testified that in his review of appellant’s x-ray he also found pleural plaques but that they were of ‘the most minimal positive category. I definitely did identify them but in very, very low quantity, very mild, very minimal.’ Id. at 14-16. He further stated that while the plaques were consistent with asbestosis, he would expect to find more of them before making a diagnosis of asbestosis. Id. at 17-18. He thus concluded that the x-rays ‘are not absolutely diagnostic of asbestosis.’ Id. at 18. Both Dr. Shively and Dr. Gardner agreed- that the x-rays showed chronic obstructive lung disease, caused, Dr. Shively stated, by smoking. Id. at 13, 107.
“As to the causes of appellant’s disability, his witnesses agreed that both asbestosis and cigarette smoking where significant factors. Dr. Sachs testified as follows:
Q. Now, Mr. Caroselli [counsel for appellant] asked you what role asbestosis played in that disability and I am going to ask you, are you able to differentiate and tell us what role the emphysema played in his disability?
A. I can’t separate these two diseases for you in terms of percentage. My opinion is that both play a significant role in this man’s disability, but I have no way of equating them or breaking them down. I can’t tell you that asbestos contributed 48% and emphysema 52%, I don’t know how to do that. There is no way I *390know of to separate these two diseases which are so closely intertwined.
I believe that both of them exist to a significant degree and they are both significant factors in this man’s disability. That is the best I can do with that.
Q. Would the impairment due to chronic bronchitis and due to emphysema be disabling?
First of all, can you answer that: Maybe you don’t know.
A. I don’t know how much emphysema he has because superimposed on the emphysema is a significant amount of pleural thickening and fibrosis in the lungs. So if we were to take those away, I don’t know if the remaining lung would be normal or not. I have no way of knowing that.
Q. Just so I understand it correctly, what you are saying is you can’t tell us the degree to which this man would be disabled solely from the chronic bronchitis and the emphysema?
A. I don’t know how to give you a percentage.
Q. However, my understanding is that it is your opinion that the emphysema and bronchitis are significant factors in whatever disability he may have.
A. That is correct.
Q. And am I correct that his longstanding cigarette smoking is a significant factor in his disability?
A. It is a factor in the sense that it enhances the genesis of bronchitis and emphysema and many people think it enhances the genesis of asbestosis. That is it enhances the fibrosis of asbestosis and certainly enhances the associated complication of asbestosis.
Q. Touching on that point while we are talking about chronic obstructive lung disease, am I correct that the cause of that disease syndrome would be Mr. Martin’s cigarette-smoking history? Would that be a cause?
A. Yes, I believe that that is the most likely affiliated factor.
*391N.T. Vol. I-A at 787-89.
“Dr. Laman testified:
Q. And do you have an opinion, Doctor, with reasonable medical certainty, whether or not his asbestosis is a substantial factor in his total and permanent disability?
A. Yes. His asbestosis is a substantial factor in his total and permanent disability.
Q. And finally, Doctor, are you able to ascribe or indicate to the jury what percentage of his disability is total and permanent disability as attributable to his asbestosis and what percentage is attributable to his cigarette smoking?
A. It is not possible for me to separate out the relative contribution of cigarette smoking and asbestos from the cause of his obstructive pulmonary disease and the cause of his total and permanent disability. Both factors are important in producing the effect and the pulmonary disability that he has.
N.T. Vol. II-A at 18-19.
It was Dr. Shively’s view that while ‘there were radiographic findings consistent with asbestosis____ [t]here was no evidence ... that the asbestos exposure ... contributed at all to [appellant’s] impairment.’ N.T. Vol. IV at 115. He gave the opinion that appellant’s disability was caused by chronic obstructive lung disease with pulmonary emphysema and chronic bronchitis, which in turn were caused by cigarette smoking. Id. at 114.”
349 Pa.Sup.Ct. 46, 51-55, 502 A.2d 1264, 1267-69 (1985).
Since the jury found appellee partially liable the majority assumes that it rejected all of Dr. Shively’s festimony. This is not necessarily the case. A jury may choose to believe all, some or none of a witness’s testimony. Weidemoyer v. Swartz, 407 Pa. 282, 180 A.2d 19 (1962). Here, the jury could have credited Dr. Shively’s testimony that appellant *392suffered substantial disability from cigarette smoking but still have believed appellant’s experts’ testimony that asbestos exposure also played a significant part.
I am at a loss to imagine what additional testimony would satisfy the majority. Requiring the experts to speak in terms of numerical percentages1 introduces a false precision into the evidence. Mathematical exactitude is not found in the real world of medicine. We should not mislead lay jurors by requiring experts to falsely imply its existence. Honest, but more flexible, words such as “substantial factor,” “major contribution” or “significant cause” are more suitable to the proper jury function of justly and fairly resolving uncertainties. It is unfair and unjust to place on appellee the whole burden of supporting appellant for a disability his own experts admit he himself substantially caused. The rule “drafted” for Section 433A of the Restatement does not reduce that injustice and the “law” written by its draftsmen, who were never elected to the legislature, finds its only authority in reason and need not be followed to an unjust result.
Indeed, properly read and applied to this case, the reason behind section 433A of the Restatement is not violated here or inconsistent with the jury verdict. The evidence favoring apportionment of damages provides a “reasonable basis” for that verdict, which simply took into account the “substantial” adverse impact appellant’s own conduct had on his condition. Determining facts from conflicting and confusing evidence like that presented here is the jury’s function. General Electric Credit Corp. v. Aetna Casualty & Surety Co., 437 Pa. 463, 263 A.2d 448 (1970); Mapp v. Wombucker, 421 Pa. 383, 219 A.2d 681 (1966). I would affirm on the opinion in Superior Court. Martin v. Owens-Corning Fiberglas Corp., 349 Pa.Sup.Ct. 46, 502 A.2d 1264 (1985).
. Appellant does not argue that experts must testify in mathematical terms about the contribution of each disease to the total disability. Such testimony is not required under our well established precedent, Osterling v. Frick, 284 Pa. 397, 131 A. 250 (1925), or by the Restatement (Second) of Torts.